IC-NR 


rsf 

S3    ' 


£&urattunal  JpriQrltnlttgii  Ulmunjrapbii 

This  volume,  which  is  No.  23  in  the  Series, 

was   prepared  under  direction  of  the  faculty 

of  New  York  University. 


PERIODIC  VARIATIONS  IN  EFFICIENCY 


PERIODIC  VARIATIONS 
IN  EFFICIENCY 

As  shown  in  Mental  and  Physical  Tests  together 
with  some  Weather  Effects 


By 
ARCHIBALD  G.   PEAKS 


BALTIMORE 

WARWICK  &  YORK,  Inc. 
1921 


Copyright,  1921,  by 
WARWICK  &  YORK,  Inc. 


PREFACE 

Many  studies  have  appeared  which  suggest  the  existence 
of  periodic  variations  in  both  physical  and  mental  activities 
during  the  year,  during  the  day,  and  in  conjunction  with 
periodic  changes  in  natural  phenomena  such  as  sunlight 
and  temperature,  but  as  yet  the  factors  involved  are  but 
little  understood.  In  order  to  assist  in  the  solution  of  these 
complex  problems,  the  author  has  attempted  the  following: 

(1)  To  give  a  complete  historical  view  of  the  experi- 
mental data  on  the  subject. 

(2)  To  examine   the  means,   methods,   and   procedure 
employed  by  other  investigators. 

(3)  To  give  a  critical  evaluation  of  the  results  of  pre- 
vious investigations  in  the  light  of  the  means  em- 
ployed, the  methods  used,  and  the  procedure  fol- 
lowed. 

(4)  To  use  improved  methods  and  procedure  in  investi- 
gating the  problems  of  periodicity. 

(5)  To  summarize  the  results  of  previous  investigators, 
and  compare  them  with  his  own. 

(6)  To  point  out  some  problems  which  future  investi- 
gators should  attempt,  and  some  errors  which  they 
should  avoid. 


488243 


CONTENTS 

Preface     , I 

I.  Growth  Rythms    • 5 

II.  Seasonal  Periodicity  in  Mental  and  Physical  Abilities 

i — Periodicity   of    Attention    (Schuyten): 9 

2 — Periodicity  in  Muscle  Strength  (Schuyten)    13 

3 — Periodicity  in  Primary  Memory  (Lobsien) 15 

4 — Periodicity  in  Strength  and  Endurance   (Lehman 

and    Pedersen)      IQ 

5— Seasonal  Variations  in  Diurnal  Periodicity    (Kuhnes)     25 
•     6 — Summary   of    Problems   and   Results    in    Seasonal 

Periodicity    . .  : 27 

III.,    An  Original  Experimental  Study  in  Seasonal  Period- 
icity 

i — Introduction    29 

2 — Periodicity    as    shown    in    Physical    Tests 29 

3— Periodicity  as  shown  in  Primary  Memory  Tests 33 

4 — Comparisons    of    Mental    and    Physical    Seasonal 

Periodicity 36 

IV.     Diurnal    Variations    in    Efficiency 

i — Introduction     48 

2 — Daily  Variations  in  Voluntary  Muscular  Contrac- 
tion   ( Storey) 49 

3 — The  Diurnal  Course  of  Efficiency   (Marsh) 50 

4 — Diurnal  Variations  and  Exercise  Effects  (Lehman 

and   Pedersen )    52 

5— Diurnal  Variations  in  Muscular  Energy  (Kuhnes) 53 

6 — Variations  in  Efficiency  During  the  Day  (Gates) 54 

7 — Diurnal   Variations    in    Memory   and   Association 

(Gates)    : 57 

8 — Summary    of    Problems    and    Results    in    Diurnal 

Periodicity 5& 

9 — Diurnal   Periodicity  in   my   Orginal   Experimental 

Investigations 59 

V. — Other  Periodic  Variations 

i — Introduction     61 

2 — Twenty-eight   Day    Periodicity 61 

3 — Twenty-three    Day    Periodicity 62 

4 — Weekly    Periodicity 63 

$ — Weekly  Periodicity  in  my  Original  Experimental 

Investigations    64 

3 


4  CONTENTS 

VI.— Weather   Influences 

I — Introduction     66 

2— General  Weather  Effects 66 

(a)  Conduct  and  the  Weather   (Dexter) 

(b)  Civilization    and    Climate     (Huntington) 68 

(c)  Effects    of    Weather    on    Ability     to      Learn 
(Lehman  and   Pedersen)    69 

3— Effects  of  Variations  in   Sunlight 70 

4 — Effects  of  Changes  in  Temperature 70 

(a)     Influence    of    Temperature    on    Rapidity    of 

Addition    (Lehman   and   Pedersen)    72 

5 — Effects   of   Variations   in    Humidity 73 

6 — Effects  of  Barometric  Changes    74 

7 — Summary   of    Problems    and  Results   in   Weather 

Effects 75 

8 — Weather    Effects    in    my    Original    Experimental 

Investigation    78 

VII.     Critical  Review  of  Experimental  Methods  in  Investi- 
gating Periodicity 

I — Introduction     82 

2 — Detailed  Discussion  of  Scientific  Method 83 

3.— Validity  of  Results    90 

VIII.— Summary    and    Suggestions Qi 

X.— Bibliography    94 


CHAPTER    I. 

GROWTH  RHYTHMS 

All  human  life  is  a  growth  involving  numerous  mental 
and  physical  changes  in  the  human  organism  from  hour  to 
hour,  day  to  day,  month  to  month,  year  to  year,  and  age 
to  age.  This  growth  was  long  considered  to  follow  a  quite 
regular  course  from  year  to  year,  except  in  individual  cases 
when  its  course  was  interrupted  by  sickness,  poor  food, 
mal-nutrition,  worry,  or  some  other  like  cause.  We  find, 
however,  a  vague  but  more  or  less  real  recognition  of  the 
more  general  periodic  changes  in  human  life  in  Hippocrates' 
division  of  life  into  seven  stages,  a  division  which  was 
later  employed  by  Shakespeare  in  his  "Seven  Ages"  of  man. 

These  general  divisions  continued  to  be  recognized  for 
'several  centuries,  though  the  depth  and  profundity  of  the 
changes  taking  place,  (especially  between  infancy  and 
childhood  and  between  childhood  and  youth),  were  but 
vaguely  comprehended.  It  is  only  with  the  growth  of 
scientific  research  along  the  lines  of  Biology,  Genetic  Psy- 
chology, Child  Study,  and  Experimental  Pedagogy  that 
their  great  significance  has  been  sufficiently  recognized. 

Besides  these,  many  other  growth  rhythms  have  been 
detected.  As  early  as  1859,  E.  Smith36  showed  in  his 
"Analysis  of  Respiration"  that  breathing  is  at  a  maximum 
in  spring  and  at  a  minimum  toward  the  end  of  the  summer 
and  beginning  of  autumn. 

Somewhat  later,  N.  Finsen10  found  that  the  amount  of 
haemoglobin  in  the  blood  also  has  periodic  variations,  show- 
ing a  maximum  in  fall  and  a  minimum  in  winter.  This 
might  be  explained  partly  by  the  corresponding  increase  or 
decrease  in  the  amount  of  air  breathed;  as  the  maximum 
amount  of  haemoglobin  comes  sometime  before  the  mini- 

5 


6  PERIODIC   VARIATIONS    IN    EFFICIENCY 

mum  of  breathing,  while  the  minimum  of  the  former  shows 
itself  a  short  time  before  the  minimum  of  the  latter. 

Following  this,  Lehman34  through  tests  with  a  plethysmo- 
graph  found  that  there  are  periodic  variations  in  the  strength 
of  heart  beats  which  agree  with  the  variations  in  the  haemo- 
globin content  of  the  blood,  in  being  greater  in  summer  than 
in  winter. 

That  the  growth  in  height  and  weight  of  the  child  under- 
goes various  periodic  changes  within  the  year  was  first  dis- 
covered by  Malling-Hansen,  director  of  the  deaf  mute  in- 
stitute in  Copenhagen.  The  occasion  for  its  discovery  was 
accidental.  In  the  year  1882,  Malling-Hansen  changed  the 
diet  of  all  the  boys  under  his  care,  and  in  order  to  discover 
the  effects  of  this  change  on  the  physical  development  of 
the  pupils,  he  hit  upon  the  expedient  of  carefully  weighing 
the  boys  daily.  This  he  did  with  130  boys  from  May, 
1882,  to  Feb.,  1886,  and  for  the  last  two  years  of  that  period 
he  also  measured  them  daily  with  much  care,  taking  elabor- 
ate precautions  to  secure  accuracy  and  uniformity  in  all 
measurements.  By  this  means  he  discovered  that  the  height 
and  weight  of  growing  boys  seemed  to  be  subject  to  periodic 
variations  which  recurred  year  after  year  in  the  same 
manner. 

Nearly  all  his  tables  in  "Perioden  im  Gewicht  der  Kinder 
und  der  Sonnewaerme"29  are  based  on  the  measurements 
and  weighings  of  about  70  boys,  from  nine  to  seventeen 
years  old,  weighed  from  May,  1882,  to  Feb.,  1886,  and 
measured  from  Feb.,  1884,  to  Feb.,  1886.  The  children 
were  weighed  four  times  per  day  with  the  exceptions  of  va- 
cations, each  of  which  lasted  six  weeks,  from  the  middle 
of  July  to  the  end  of  August.  The  pupils  were  weighed  in 
groups  of  sixteen  to  eighteen,  and  the  heights  given  are  also 
of  these  groups.  His  data,  therefore,  show  nothing  as  to 
changes  in  individuals.  His  results  may  be  summarized  as 
follows :  The  weight  of  a  group  of  growing  boys  from  nine 


GROWTH  RHYTHMS  7 

to  sixteen  years  of  age,  has  three  periods  of  growth  during 
the  year, — a  maximal,  a  middle,  and  a  minimal.  The  maxi- 
mal period  begins  in  August  and  ends  in  the  middle  of 
December,  lasting  four  and  one-half  months.  The  minimal 
period  extends  from  the  end  of  April  to  the  end  of  July,  last- 
ing three  months.  During  the  maximal  period,  the  rate  of 
increase  is  three  times  as  great  as  in  the  middle  period. 
Almost  the  whole  weight  gained  in  the  middle  period  is  lost 
in  the  minimal  period. 

Respecting  growth  in  height,  he  finds  that  the  minimal 
period  begins  in  August  and  lasts  till  the  middle  of  Novem- 
ber, three  and  one-half  months.  The  middle  period  reaches 
from  the  end  of  November  till  the  end  of  March,  about  four 
months.  The  maximal  period  extends  from,  the  end  of 
March  to  the  middle  of  August,  about  four  and  one-half 
months.  The  daily  rate  of  gain  in  height  in  the  maximal 
period  is  two  and  one-half  times  as  great,  and  in  the  middle 
period  is  twice  as  great  as  that  of  the  minimal  period. 

It  is  also  interesting  to  note  here  that  Dr.  Winifred  Hall, 
of  Haverford  College,  develops  the  same  law  of  separate 
rhythms  for  height  and  weight  during  the  larger  periods  be- 
fore and  during  pubescence  that  Malling-Hansen  found 
for  the  seasons.  Dr.  Hall  finds  that  when  the  vertical  dimen- 
sions of  the  body  are  undergoing  acceleration  of  their  rate 
of  growth,  the  horizontal  undergo  a  retardation  of  their 
growth,  and  conversely.  The  same  author  also  claims  that 
growth  in  height  is  due  largely  to  an  increase  in  length  of  the 
long  bones.  G.  Stanley  Hall  claims  that  adults  tend  to  grow 
thin  when  children  grow  tall,  and  to  grow  thick  when  chil- 
dren grow  heavy;  and  suggests  that  by  using  the  former 
period  for  cures,  fleshy  people  can  aid  nature. 

Many  other  annual  or  seasonal  rhythms  of  life  are  known 
to  science,  among  the  more  common  of  which  we  find  the 
migration  of  birds,  the  hibernation  of  various  animals,  the 
running  of  fishes,  the  shedding  of  winter  coats  of  fur  and 


8  PERIODIC   VARIATIONS    IN    EFFICIENCY 

feathers,  and  the  mating  season  of  animals  of  all  sorts. 
We  see,  therefore,  that  Malling-Hansen  was  in  the  presence 
of  a  great  biological  law  of  rhythmic  growth  which  depends 
for  its  existence  on  the  very  nature  of  the  universe  itself. 
The  findings  of  Malling-Hansen  have  been  corroborated 
in  the  main  by  Dr.  Schmidt-Monnard  in  Halle,  Germany. 
Besides  this,  various  supplements  to  these  investigations 
have  been  made,  regarding  the  periodicity  of  mental  and 
physical  development,  and  the  periodic  changes  in  mental 
and  physical  abilities,  which  seek  to  discover  the  nature  of 
any  existing  paralellisms  in  physical  and  psychic  functions 
and  to  discover  the  probable  causes  of  their  periodic  varia- 
tions. A  full  account  of  such  investigations  will  be  given  in 
the  following  pages. 


CHAPTER  II. 

SEASONAL  PERIODICITY  IN  MENTAL  AND  PHY- 
SICAL ABILITIES. 

i.     PERIODICITY   OF   ATTENTION.     (SCHUYTEN) 

(1)  Method.     During  the  school  year  1893-4,  Dr.  M.  C. 
Schuyten,  director  of  the  pedagogical  laboratory  at  Antwerp, 
made   a   series   of   investigations    concerning   the    periodic 
variations  in  the  power  of  attention.     The  following  data 
are  taken  from  a  report  of  his  work  given  by  Marx  Lob- 
sienjn  his  "Schwankungen  der  Psychischen  Kapazitat." 

Two  upper  and  two  lower  classes  of  boys  and  girls  from 
eight  to  ten  years  of  age  were  tested  monthly  to  discover 
any  periodic  variations  in  their  power  of  attention.  The 
children  were  tested  four  times  on  each  test  day.  To  avoid 
any  disturbance  from  other  classes,  those  to  be  tested  were 
isolated  during  the  tests. 

Each  child  sat  with  his  Flemish  reader  open  before  him. 
At  a  given  signal  which  always  remained  the  same,  the  chil- 
dren began  to  read  silently.  The  experimenter  noted  by  ob- 
servation those  who  were  not  attentive,  those  who  stopped 
reading,  those  who  raised  the  eyes  from  the  pages,  and 
those  who  were  continuously  attentive  through  five  minutes, 
the  length  of  the  test.  The  investigation  was  begun  in 
March,  1893,  and  continued  for  one  year  except  during  the 
months  of  August  and  September,  when  the  long  vacation 
intervened. 

(2)  Results.     The  general  summary  of  the  results  for 
the  year  is  here  given: 

Month      Jan.  Feb.  Mch.  Apr,  May.  Jun.  July  Oct.  Nov.  Dec. 
Per  cent,  of 
Attention 

Energy     68      63      77      69      64      42      27      48      62      67 

9 


IO  PERIODIC   VARIATIONS    IN    EFFICIENCY 

He  notes  the  greatest  difference  between  March  and  July. 
Upon  these  results  he  bases  the  following  conclusions : 

1.  The  power  of  attention  in  children  is  inversely  pro- 
portional to  the  atmospheric  temperature. 

2.  It  is  greater  in  the  higher  than  in  the  lower  classes. 

3.  It  is  greater  in  girls  than  in  boys. 

4.  It  diminishes  from  8:30  a.  m.  to  11:00  a.  m.,  and 
again  from  2.00  p.  m.  to  4:00  p.  m.,  but  it  is  always 
greater  at  2  :oo  p.  m.  than  at  1 1  :oo  a.  m.,  and  less 
than  at  8  .'30  a.  m. 

(3)  Verifying  Tests.  In  order  to  satisfy  himself  that 
the  results  were  valid,  Schuyten  made  a  second  set  of  ex- 
periments using  the  same  general  method  of  study  as  before 
with  one  exception,  he  began  the  tests  in  April  instead  of 
March.  The  final  summary  of  the  results  from  the  verifying 
tests  is  here  given : 

Month      Jan.  Feb.  Mch.  Apr.  May  Jun.  July  Oct.  Nov.  Dec. 
Per  cent,  of 
Attention 
Energy      59      54      54      5*      45      42      35      48      51      57 

Various  comparative  tables  are  given  some  of  which  are 
here  reproduced : 

TESTS  TAKEN  AFTER  A  REST 

Month          Jan.  Feb.  Mch.  Apr.  May  Jun.  Jul.  Oct.  Nov.  Dec. 
Per  Cent. 

A.  M.         64      59      57      55      47      45      39      52      55      62 
P.  M.          59      55      57      52      49      47      42      50      51       5« 
TESTS  TAKEN  BEFORE  AND  AFTER  A  REST 
Month          Jan.  Feb.  Mch.  Apr.  May  Jun.  Jul.  Oct.  Nov.  Dec. 
Per  Cent. 

Before   Rest         56      51      50      43      42      36      29      46      48      55 
After  Rest  61       57      57      53      49      46      40      5i      53      60 

TESTS  AFTER  REST,  HIGH  AND  LOW  CLASSES' 
Month          Jan.  Feb.  Mch.  Apr.  May  Jun.  Jul.  Oct.  Nov.  Dec. 
Per  Cent. 

High  Class  61      56      55      52      49      47      41      52      52      59 

Low  Class  61      57      49      54      4§      45      AP      &      54      60 


SEASON AI,  ' PERIODICITY    IN    ABIUTlES  II 

TESTS  AFTER  REST,  BOYS  AND  GIRLS 

Month          Jan.  Feb.  Mch.  Apr.  May  Jun.  Jul.  Oct.  Nov.  Dec. 

Boys  61      56      57      54      49      45      41       50      53  60 

Girls  61      58      57      53      41      46      40      51      53  59 

From  these  results  Schuyten  concludes : 

1.  That  the  results  of  the  first  experiment  are  verified 
by  the  second, 

2.  Rest  has  a  good  influence  on  attention. 

3.  In  winter,  a  higher  per  cent,  is  obtained  after  the 
morning  rest  than  after  the  afternoon  rest ;  in  sum- 
mer the  reverse  is  true.    This  would  show  that  inter- 
missions   are   more   beneficial    in   summer   than    in 
winter. 

4.  Recess  periods  have  more  influence  on   the  lower 
classes  than  on  the  higher  classes. 

5.  Recess  periods  are  more  beneficial  to  boys  than  to 
girls. 

(4)  Criticism.  This  work  by  Schuyten  is  a  pioneer  in 
its  field  and  as  such  deserves  great  credit.  There  are  sev- 
eral probable  sources  of  error,  however,  on  the  basis  of 
which  we  may  question  the  universal  validity  of  his  re- 
sults. The  first  is  in  regard  to  the  means  employed.  It  is 
entirely  probable  that  the  pages  used  in  the  Flemish  readers 
were  not  equally  interesting  to  all  the  children  in  the  differ- 
ent classes  so  that  the  material  lacked  uniformity.  Schuyten 
himself  admits  that  this  may  be  true. 

There  may  also  be  a  question  raised  as  to  the  usefulness 
of  the  method  of  recorded  observation  in  measuring  the  at- 
tention of  children  in  a  large  group.  The  author  judged 
only  by  appearances  without  checking  the  results  by  the 
introspection  of  the  children.  Aside  from  the  fact  that 
these  results  do  not  easily  lend  themselves  to  quantitative 
measurements,  it  is  possible  that  many  times  only  the  signs 


12  PERIODIC    VARIATIONS    IN    EFFICIENCY 

of  attention  were  mistaken  for  the  fact  of  attention. 
Schuyten  had  his  doubts  about  this  point,  and  Lobsien 
doubted  so  strongly  that  he  devised  a  new  method  which 
aimed  at  uniformity  of  material,  and  gave  a  record  which 
lent  itself  more  readily  to  quantitative  measurement. 

In  regard  to  the  results  from  Schuy ten's  "Verifying 
Test,"  I  can  scarcely  agree  with  him  that  it  proves  the 
results  of  the  first  experiment.  It  seems  to  me  that  in 
Schuyten's  first  tests,  we  see  in  the  high  level  for  March 
the  effects  of  novelty  rather  than  a  true  index  of  the  ability 
or  power  of  attention.  This  shows  the  great  need  for  pre- 
liminary tests  in  any  experimental  investigation  in  order 
to  perfect  the  method,  and  to  eliminate  practice  effects.  As 
none  were  given,  it  seems  reasonable  to  suppose  that  the  re- 
sults of  the  verifying  test  give  a  truer  range  of  the  varia- 
bility of  attention  than  do  the  results  from  the  first  set  of 
tests.  These  later  results  seem  to  show  a  crest  in  January 
rather  than  in  March. 

Concerning  his  conclusions  for  age  and  sex  differences, 
though  we  grant  the  validity  of  his  results,  the  resulting 
differences  are  not  large  enough  or  persistent  enough  to 
be  the  basis  for  any  such  general  conclusions  as  he  has  made. 

Finally,  Schuyten  is  not  warranted  in  drawing  any  such 
sweeping  conclusions  from  four  tests  made  on  the  same 
day,  and  once  each  month.  The  work  of  other  investigators 
shows  that  the  records  from  such  a  small  number  of  tests 
per  month  contain  many  accidental  errors  which  tend  to 
minimize  the  validity  of  the  results,  so  that  what  seems  to  be 
seasonal  variations  may  be  due  in  a  large  part  to  accidental 
causes. 

The  results  from  these  experiments  are  shown  graphically 
in  Fig.  2,  where  they  are  compared  to  his  results  on  period- 
icity in  muscular  energy. 

2.  PERIODICITY  IN  MUSCLE  STRENGTH.    (SCHUYTEN) 

(i)     Method.     Schuyten  next  tried  by  experiments  to 


SEASONAL    PERIODICITY    IN    ABIUTlKS  13 

discover  the  annual  variations  in  and  the  annual  increase 
of  muscle  strength  in  boys  and  girls.  Accordingly  he  tested 
the  grip  strength  of  a  group  of  children  of  both  sexes  in 
Antwerp  during  the  school  year  from  October,  1898,  to 
July,  1899.  These  tests  were  given  on  the  fifteenth  of  each 
month  at  2:15  p.  m.  In  all  5400  results  were  tabulated. 
The  Elliptical  Dynamometer  was  used  for  both  pushing  and 
pulling  tests,  first  with  the  right  and  then  with  the  left  hand. 
The  children  were  encouraged  to  wager  so  they  would  use 
all  their  strength. 

(2)  Results.    The  following  table  shows  the  results  for 
both  sexes,  pushing  and  pulling : 

Month  Oct.  Nov.  Dec.  Jan.  Feb.  Mch.  Apr.  May  Jun.  Jul. 

Pull  438  469  487  491  511  490  515  534  558  582 

Boys 

Push  139  149  155  156  162  156  1 66  170  178  185 

Pull  439  436  452  453  486  481  481  481  488  506 

Girls 

Push  138  139  144  144  155  155  153  154  155  161 

Pull  436  455  469  474  497  486  499  509  $24  547 

Both 

Push  139  145  149  151  158  155  159  162  167  174 

One  result  which  is  everywhere  shown  is  the  downward 
curve  of  capacity  in  March,  only  one  case  showing  a  slight 
increase.  Commenting  on  this  the  author  gives  the  follow- 
ing table  which  shows  the  monthly  increase  or  decrease  in 
physical  strength : 

MONTHLY  INCREASE  OR   DECREASE  IN  PHYSICAL 

STRENGTH  (Lobsien) 

Month  Oct.  Nov.  Dec.  Jan.  Feb.        Mch.  Apr.  May  Jun.  July 

Boys  —      3.1       1.6      04      1.9      — 2.0      2.6  1.9      2.4      24 

Girls  —      0.3      1.0      o.i      0.5      —0.5      o.o  0.2      0.6      1.8 

Average       —      1.8      1.6      o.i      2.4      — i.i       1.3  i.o      1.5      2.3 

(3)  Verification.      Not   wholly   satisfied    with   these,  re- 
sults Schuyten  made  a  supplement  to  them  in  the  year  fol- 
lowing.    In  this  investigation  he  tried  to  eliminate  the  ef- 


14  PERIODIC   VARIATIONS    IN    EFFICIENCY 

fects  of  growth  and  habit  by  testing  a  different  group  of  chil- 
dren each  month.  In  several  public  schools  of  Antwerp,  he 
grouped  the  children  according  to  the  month  in  which  they 
were  born.  Each  child  began  the  tests  at  the  age  of  nine 
years  and  nine  months,  those  born  in  January  being  tested 
in  October,  those  born  in  February  being  tested  in  Novem- 
ber, etc.  Each  monthly  group  was  tested  three  times  during 
the  first  half  of  the  month,  first  with  the  left  hand  and  then 
with  the  right  hand.  The  results  from  45,453  records  are 
shown  in  the  tables  below.  These  tables  show  the  average 
pulling  strength  for  both  hands  combined.  The  children 
in  the  first  table  were  born  in  the  year  1889,  and  those  in  the 
second  table  were  born  in  1890. 

1889                          ,  1890 

Month  Boys  Girls  Aver.  Month  Boys  Girls  Aver. 

Jan.  47.0  38.4  43-0  Jan.  39.9  34- 1  36.6 

Feb.  44.1  38.7  41-3  Feb.  38.4  34-3  36.1 

Mch.  44.9  36.0  38.8  Mch.  35.9  32.8  34.3 

Apr.  46.9  37-9  41-8  Apr.  39.1  34-O  36.3 

May  47.0  38.6  42.7  May.  41.2  33.9  38.4 

Jun.  50.6  40.1  46.0  Jun.  43.5  35.7  38.7 

Jul.  49.9  39-8  44.4  Jul.  44.3  36.4  39.5 

Oct  44-1  36.2  39.1  Oct.  38.2  32.6  35.1 

Nov.  45.7  37.2  40.9  Nov.  38.0  33.1  35.3 

Dec.  46.5  38.1  42.4  Dec.  39.5  34- 1  36.6 

From  the  results  of  these  two  investigations,  Schuyten 
concludes  that  there  are  four  distinct  periods  for  muscular 
energy  as  follows: 

1.  A  falling  period  from  January  to  March, 

2.  A  rising  period  from  April  to  June, 

3.  A  decrease  from  July  to  September, 

4.  An  increase  from  October  to  December. 

(4)  Criticism.  Of  these  two  investigations  concerning 
periodicity  in  muscular  energy,  Schuyten  bases  his  con- 
clusions almost  entirely  on  the  second  or  verifying  test.  Of 
course  it  is  true  that  the  effects  of  practice  and  of  yearly 
growth  are  largely  eliminated  by  this,  and  the  results  from 


PERIODICITY    IN    ABlUtlES  15 

the  different  months  are  comparable.  The  only  drawback  is 
that  the  groups  tested  were  not  homogeneous  or  uniform, 
and  the  individual  differences  found  might  destroy  the  value 
of  the  most  important  variations  shown  in  the  results. 

While  recognizing  that  this  criticism  might  be  made, 
Schuyten  minimizes  its  effect,  and  entirely  neglects  it  in 
drawing  his  conclusions.  A  series  of  preliminary  tests 
made  on  the  monthly  groups  might  have  been  arranged  so 
that  the  individual  differences  could  have  been  almost  en- 
tirely eliminated.  That  no  such  preliminary  tests  were 
given  seems  very  unfortunate,  and  casts  the  only  doubt  on 
what  is  otherwise  a  very  carefully  conducted  experiment. 
£  -3.  PERIODICITY  IN  PRIMARY  MEMORY.  (LOBSIEN) 

(1)  Method.     Lobsien  criticised  Schuyten's  conclusions 
on  the  grounds  ( I )  that  the  tests  were  not  homogeneous  or 
of  the  same  degree  of  difficulty,  and  (2)  that  the  variations 
noted  in  the  tests  are  not  entirely  due  to  changes  of  the 
seasons  or  to  changes  in  the  atmospheric  temperature.     He 
therefore  sought  to   supplement   and  verify   the   work   of 
Schuyten  in  a  similar  investigation.    In  gathering  the  data, 
experiments  were  made  on  boys  and  girls   in  the   public 
schools  of  Kiel,  Germany,  from  8  to  14  years  of  age.    They 
were  made  on  the  fifteenth  day  of  each  month  from  Septem- 
ber, 1901,  to  June,  1902,  July  and  August  being  vacation 
months. 

(2)  Procedure.     Lobsien's  work  is  limited  to  the  study 
of  primary  memory  for  lists  of  ten  words  involving  both 
visual  and  auditory  imagery,  which  are  here  reproduced: 

LOBSIEN'S  WORD  LISTS 
VISUAL  ACOUSTIC 

A  A 

1.  Sonnenlicht  i.  Gesang 

2.  Fensterscheibe  2.  Gebell 

3.  Wandteller  3.  Summen 

4.  Handspiegel  4.  Sausen 

5.  Himmelblau  5.  Rasseln 


16 


PERIODIC   VARIATIONS    IN    EFFICIENCY 


6.  Abendstern 

7.  Taubenhaus 

8.  Ofenschirm 

9.  Turmuhr 
10.  Bierglas 

B 

1.  Abendrot 

2.  Brieftasche 

3.  Federbusch 

4.  Fensterkreuz 

5.  Feuerwerk 

6.  Handschrift 

7.  Mondscheibe 

8.  Gotteshaus 

9.  Kirchtum 
10.  Streichholz 

C 

1.  Kohlschwarz 

2.  Morgenstern 

3.  Xachtmutze 

4.  Olzweig 

5.  Ofenrauch 

6.  Rotfuchs 

7.  Freimarke 

8.  Angesicht 

9.  Vorschrift 
10.  L,ampenglas 

D 

1.  Feuerschein 

2.  Morgenrote 

3.  Leuchtkeugel 

4.  Postkarte 

5.  Schattenbild 

6.  Blitzstrahl 

7.  Georgine 

8.  Spiegelbild 

9.  Zifferblatt 

10.  Hangenlampe 


6.  Lispeln 

7.  Poltern 

8.  Lai-men 

9.  Donnern 
10.  Sprechen 

B 

1.  Drohnen 

2.  Stampfen 

3.  Krachen 

4.  Bellen 

5.  Sauseln 

6.  Rauschen 

7.  Knistern 

8.  Klirren 

9-  Kreischen 

10.  Blasen 
C 

1.  Ticken 

2.  Weihern 

3.  Meckern 

4.  Gackern 

5.  Krahen 

6.  Briillen 
7-  Klingen 

8.  Pfeifen 

9.  Trommeln 
10.  Klappern 

D 

1.  Zirpen 

2.  Rufen 

3.  Weinen 

4.  Scharren 

5.  Seufzen 

6.  Knallen 

7.  Puffen 

8.  Schluchzen 

9.  Winseln 
10.  Klopfen 


The  word  lists  were  spoken  plainly  after  which  each  pupil 
was  asked  to  write  the  words  in  a  list  at  once.  Lobsien  tab- 
ulated the  results  separately  for  girls  and  boys  and  for  each 
age. 

(2)     Results.    The  results  as  shown  in  the  accompanying 


SEASONAL    PERIODICITY    IN    ABILITIES  17 

tables  include  8900  records  and  the  experiments  are  based 
on  two  important  activities  of  the  mind,  primary  memory  and 
attention.  The  result  are  here  given: 

GIRLS 

Month  Visual  Imagery     Auditory  Imagery 

September  2386  2515 

October  2489  2138 

November  3964  2605 

December  2686  2257 

January  2980  2325 

February  2810  2322 

March  .      2847  2761 

• '  >  April  2483  2262 

May  2640  2641 

June  2523  2530 

BOYS 

Month  Visual  Imagery     Auditory  Imagery 

September  2328  2492 

October  2073  1894 

Novembber  2063  2218 

December  2142  2243 

January  2053  2319 

February  (1965  Estimated)     (1968) 

March  (2102  Partly  lost)  (2161) 

April  2011  2266 

May  2246  2400 

June  2384  1967 

The  curves  for  boys  and  girls  are  much  alike.  The  mid- 
dle energy  height  is  much  higher  for  girls  than  for  boys.  In 
general  these  curves  show  a  high  period  or  crest  around 
December  and  January,  and  a  trough  or  depression  in  Feb- 
ruary and  April.  The  visual  tests  show  a  curve  which  is 
higher  in  the  first  part  than  in  the  last  part,  a  fact  which 
he  considers  the  more  remarkable  because  the  pupils  should 
improve  with  practice.  The  acoustic  curve  for  girls  in 
general  parallels  the  visual  curve,  but  always  has  a  smaller 
value.  There  is  very  little  difference  in  ages,  except  that 
psychic  energy  tends  to  become  more  uniform  with  age. 

The  results  for  boys  show  the  highest  value  in  the  first 
tests  in  September,  and  at  the  end  of  the  tests  in  June.  A 


l8  PERIODIC   VARIATIONS    IN    EFFICIENCY 

second  slight  elevation  is  found  in  January.  The  visual 
curve  is  nearly  always  less  for  boys  than  the  auditory  curve, 
and  the  variations  are  more  opposite  than  parallel.  Boys 
agree  with  girls  in  the  depression  in  the  visual  curve  around 
July.  They  also  agree  with  girls  in  showing  a  high  value  in 
December  and  January  and  corresponding  depressions  in 
February  and  April.  The  first  half  of  the  year  seems  the 
best  for  boys.  On  the  whole,  psychic  energy  is  higher  for 
girls  than  for  boys,  but  boys  show  a  higher  low  point  than 
girls. 

The  table  showing  the  monthly  changes  in  psychic  capac- 
ity shows  almost  a  regular  rise  and  fall  for  the  months  fol- 
lowing each  other  for  the  girls,  while  for  the  boys,  the 
rhythmic  changes  extend  over  a  somewhat  longer  period. 

(3)  Criticism.  The  work  of  Lobsien  while  very  care- 
fully worked  over  seems  to  be  somewhat  questionable  both 
in  the  materials  and  the  procedure.  While  the  method  was 
new,  the  word  materials  are  so  much  alike  in  form  that  the 
memory  images  undoubtedly  interfered  with  one  another. 
A  careful  survey  of  the  word  lists  will  bear  out  this  state- 
ment. Then  again,  there  are  so  many  accidental  factors  which 
enter  into  mental  abilities,  due  to  time  of  day,  temperature, 
individual  daily  results,  etc.,  that  it  is  doubtful  in  the  ex- 
treme that  the  results  from  tests  made  but  once  per  month 
are  a  true  index  of  any  but  accidental  factors,  and  that  the 
seasonal  rhythms  cannot  be  discovered  from  tests  taken  but 
once  per  month.  The  mere  fact  that  such  a  large  number  of 
persons  was  tested  cannot  overcome  this  source  of  error  in 
the  procedure.  The  validity  of  his  conclusions  that  "Physical 
and  physic  development  do  not  parallel/'  is  destroyed  by 
the  errors  in  the  data. 

4.  PERIODICITY   IN    PHYSICAL   STRENGTH.    (LEHMAN 
AND  PEDERSEN) 

(i)     Aim.     Lehman  and   Pedersen  made  a  much  more 
careful  study  of  periodicity  than  either  Schuyten  or  Lobsien. 


SEASONAL    PERIODICITY    IN    ABILITIES  1Q 

By  means  of  a  long  series  of  experiments  they  attempted  to 
discover  the  effects  of  the  weather  on  muscle  strength.  As 
the  experiments  covered  a  period  of  nearly  two  years,  many 
of  the  data  show  seasonal  variations.  We  will,  therefore, 
describe  the  more  general  variations  here,  reserving  only 
some  of  the  details  for  the  section  on  weather  effects.  The 
experiments  were  made  partly  on  public  school  pupils  in 
Copenhagen,  and  partly  on  three  grown  people.  As  the 
apparatus  and  procedure  used  for  the  children  was  different 
from  that  used  for  the  adults,  I  will  describe  the  method  and 
procedure  for  each  group  by  itself. 

(2)  The    Individual    Tests.     Most    of    the    individual 
tests  were  made  by  three  persons,  Dr.  Lehman,  Dr.  Peder- 
sen, and  Miss  J.    Each  used  the  same  individual  dynamome- 
ter throughout  the  tests,  one  being  provided  for  each.     As 
the  dynamometers  differed,  no  comparisons  were  made  be- 
tween the  results,  these  being  referred  to  as  I,  II,  and  III. 
In  the  tests,  each  person  always  used  his  own  dynamometer, 
Miss  J.  Ill,  Pedersen  II,  and  Lehman  I.     The  tests  were 
taken  always  with  the  left  hand  by  Lehman  and  Miss  J.  and 
with  the  right  hand  by  'Pedersen,   who   was   left  handed. 
Five  tests  were  made,  with  not  less  than  thirty  seconds  be- 
tween, immediately  after  rising  each  day. 

(3)  The  School  Tests.    In  the  School  Tests,  five  groups 
of  children  were  used. 

Group  I,  consisted  of  twenty-one  pupils  between  12  and 
13  years  of  age.  This  group  was  tested  one  day  (always  the 
same  day)  each  week,  between  9  a.  m.  and  10  a.  m.,  on  each 
test  day  from  January  I  to  April  21,  1904. 

Group  II,  consisting  of  twenty-one  pupils  between  10  and 

11  years  of  age,  were  tested  once  each  week  as  above  from 
August  12,  1904,  to  March  31,  1905. 

Group  III,  consisting  of  eighteen  pupils  between  n  and 

12  years  of  age,  were  similarly  tested  once  each  week  from 
August  12,  1904  to  March  31,  1905. 


2O  PERIODIC   VARIATIONS   IX    EFFICIENCY 

Group  IV,  consisting  of  the  twenty-one  pupils  between 
13  and  14  years  of  age,  were  tested  between  9  a.  m.  and 
10  a.  m.  once  each  week  from  August  12,  1904,  to  March 
3i,  1905- 

Group  V,  consisting  of  ten  pupils  between  12  and  13 
years  of  age,  were  tested  between  10  a.  m.  and  12  m.  on 
each  school  day  from  January  12,  1906,  to  June  i,  1906,  and 
again  from  August  12,  1906  to  December  21,  1906. 

In  these  tests,  Lehman's  Ergograph  was  used.  The  tests 
were  carefully  controlled  and  the  children  were  urged  to 
compete  with  each  other  for  high  records.  Before  taking 
the  tests  each  boy  was  asked  to  dry  his  hand  on  a  towel. 
Each  boy  then  took  four  grips  with  an  interval  of  four 
seconds  between  at  a  uniform  tempo.  The  averages  of  these 
four  trials  are  shown  in  the  tables  for  results.  Each  boy 
used  only  his  most  dextrous  hand  in  making  records. 

Before  the  real  tests,  each  boy  was  allowed  to  make  a 
number  of  trials,  so  as  to  learn  to  grip  in  a  uniform  tempo, 
which  was  the  same  for  all  so  far  as  possible.  Whenever  a 
pupil  was  absent,  ill,  or  otherwise  indisposed,  or  did  not 
wish  to  grip  (which  happened  very  seldom),  an  average 
grip  was  worked  out  for  him  from  the  days  preceding  and 
following,  and  put  in  its  place.  Pupils  who  were  absent 
for  a  long  period  were  not  included  in  tabulating  the  results. 

(4)  Results.  The  more  general  of  the  results  from  the 
individual  tests,  are  as  follows : 

The  curve  of  Lehman  (who  was  47  years  old),  "sinks  in 
the  fall  to  the  middle  of  December,  then  rises,  first  slowly, 
then  more  quickly  to  the  end  of  June.  It  sinks  during  July 
and  August,  rises  abruptly  in  September,  and  sinks  grad- 
ually to  the  end  of  the  tests  in  December." 

The  curve  of  Pedersen  (who  was  36  years  old),  is  very 
"similar  to  that  of  Lehman  during  most  of  the  time." 

The  curve  of  Miss  J.  (who  was  18  years  old),  and  Group 
V  of  the  boys,  who  were  also  tested  from  January  to  Decem- 


SEASONAL    PERIODICITY    IN    ABILITIES  21 

her,  "show  stationary  periods  where  Lehman  and  Pedersen 
show  a  decrease,"  and  a  continuous  rise  through  the  re- 
mainder of  the  year. 

The  results  from  each  of  the  groups  of  boys  are  presented 
in  the  following  table.  In  this  table  the  values  for  the  five 
groups  of  boys  are  given  in  kilograms,  for  each  age  sep- 
arately. They  are  also  combined  and  worked  out  in  per 
cent.,  the  January  values  being  taken  as  the  base,  and 
compared  with  light  strength  and  with  variations  in 
temperature. 

TABLE    I 

Date     Phot.    L.      P.      J.    Boys       Date  Phot.  L.      P.     J.  Boys 

Oct.     i     35.2  38.5                              May     19  467  40.6  51.5  41.3  32.0 

ii     36.2  38.2                              jun.      g  47.8  42.7  50.3  44.8  32.1 

I     2I     337  38.1                                  »       l8  48.6  42.8  50.4  46.3  33-0 

Nov  m     «1  3/7"o  "      28      45'8  43'3  5°'3  45'°  337 

°  46.0-4I.95I.047.2 


»     30    259376  l8  44.942.050.545-8 

Dec.  10    25.6  37.0                   •  281  49.  i  41.6  53-O  43-2 

"     20    25.4  37.3                              Aug.  7  47.9  41.3  53.3  46.6 

"     30    26.9  38.7  17  454  40.1  53-8  46.6   33.0 

Jan.     9    24.0  37-9  27  48.1  41.3!  52.7  46.5  33.7 

19    27.8  38,3                               Sept.  6  44.8  43.7  52.3  46.1  34.1 

29    28.1  37-7  42.4            26.2        »  l6  41.6  46.8  52.5  47-9  33-9 

Feb.    8    31-5  38.9  44-2            27.6        »  ^  41  0  45>3  500  409  34-3 

18  29.7  3te  47-8           27.8    Qct  6  g      jr               8 

28  34-6  39-5  49-1            29.2        „  ,  ^     ^  «  ^      ^       £ 
Mh.  10    35.5  39-8  50.7            29.5     -,,  2  ^3  £°  53-7  49-9  34-3 

"     20    36.4  39.2  51.7            30-3     AT  26  3°'5  43'7  5I'6  4g'°  36'4 

"      30    41-4  40.5  52.i    37.2  30.5     Nov-  5  29.0  43.7  5i.5  48.3  37-3 

Apr.    9    45-3  41.0  5^9   38.7  3^3  X5  32.8  44.1  52.4  4&7  36-9 

19  37-5  40.5  53-1    38.4  30-5  25  3^-0  43-0  52.3  SLI  37-2 

29  43.4  40.5  52.6   42.0  311.4     Dec.  5  29.1  42.5  52.6  51.5  37.0 
May   9    47-4  40.1  55-6   42.9  3i-8  15  28.3  42.0  52,1  49.2  37.2 

29      43-3  42JO  50.2  41.1  33.1  25  -42.0 

The  above  table  shows  the  weekly  averages  of  Leh- 
man, Pedersen,  Miss  J.,  and  Group  V  of  the  boys  when 
compared  to  changes  in  the  strength  of  sunlight  as  recorded 
by  a  Steenstrup  photometer. 


22 


PERIODIC   VARIATIONS    IN    EFFICIENCY 


TABLE    II 

1904 

1904 

1904    1903 

All 

11-12 

13-14 

12-13    12-13 

PerC 

Temp. 

Light 

737 

IO.2 

45-8 

24.2 

27.0 

80.3 

14.5 

47-4 

16.1 

46.7 

257 

28.6 

86.0 

15.7 

47.1 

25-8 

27.9 

844 

12.8 

42-5 

29-3 

31.8 

95-3 

8.0 

34-3 

29.6 

33-9 

100.3 

3-7 

28.7 

29.8 

33-9 

100.7 

0.8 

26.0 

29.2 

33-9 

22.7      25.9 

100.0 

—  O.I 

26.6 

29.6 

35-2 

23.0      27.9 

103.6 

o.o 

3L9 

31-2 

36.6 

25.6      29.8 

109.7 

1.2 

37.8 

254      3LO 

115.8 

57 

41.7 

32.1 

124.0 

IO.2 

45-8 

33-1 

127.7 

14-5 

47-7 

16.1 

46.7 

33-5 

129.3 

157 

47.i 

34-1 

131-6 

12.8 

42-5 

35-5 

137.0 

8.0 

35-9 

37-2 

143-5 

3-7 

30.6 

37-1 

143-2 

0.8 

28.7 

1904 

Month  lo-n 

May  19.6 

June  21. o 

July 

Aug.  22.8 

Sept.  22.0 

Oct.  25.6 

Nov.  26.5 

Dec.  26.6 

Jan.  26.6 

Feb.  27.6 

Mch.  28.2 

Apr. 
May 
June 
July 
Aug. 
Sept. 
Oct. 
Nov. 
Dec. 

The  authors  describe  the  results  by  saying  that  muscle 
strength  begins  to  rise  in  January,  with  light  strength,  and 
shows  a  decided  growth  through  February  and  March,  while 
the  temperature  is  almost  constant,  and  much  lower  than 
that  at  which  muscle  growth  stopped  in  November.  It 
still  grows  in  May,  when  light  has  attained  its  maximum, 
but  in  June  and  especially  in  July  and  August,  when  heat 
reaches  its  maximum,  growth  in  muscle  strength  stops  en- 
tirely, and  starts  again  in  September,  as  soon  as  the  heat 
decreases  somewhat.  The  fact  of  increasing  muscle  strength 
with  falling  temperature  was  noted  in  both  Lehman  and 
Pedersen,  but  in  growing  persons  the  growth  hides  this 
effect. 

The  conclusions  are  as  follows:  "The  stronger  light  is, 
the  more  favorable  the  actinic  rays  are  to  muscle  strength. 
Hea.t  ha.s  an  individually  varying  and  perhaps  a  movable 


SEASONAL    PERIODICITY    IN    ABILITIES  23 

optimum  so  that  both  low  and  high  temperatures  are  de- 
pressing to  muscle  strength.  From  the  joint  influence  of 
these  two  factors  there  arises  the  yearly  periodical  variations 
of  muscle  strength." 

(5)  Criticism.  This  work  is  very  carefully  and  sys- 
tematically done.  It  seems  possible,  however,  that  the  au- 
thors were  a  little  over-zealous  in  attempting  to  explain  the 
phenomena  of  variations  in  muscle  strength  as  due  en- 
tirely to  external  conditions.  As  to  its  aim,  means  and 
methods  of  procedure,  there  is  very  little  to  criticise.  The 
results,  also,  are  given  in  detail,  so  there  may  be  no  question 
concerning  them.  It  seems,  however,  that  the  authors  have 
drawn  conclusions  not  wholly  warranted  by  the  facts. 

In  the  first  place,  the  authors  find  a  "very  abrupt  rise  in 
muscle  strength  in  September."  This  seems  to  be  a  little 
unusual  and  needs  analysis.  Of  the  four  sets  of  records, 
shown  in  the  first  table,  but  one  person,  Lehman,  shows 
such  a  tendency.  Most  of  the  groups  of  boys  in  the  second 
table  show  a  drop  in  September,  a  large  rise  in  October,  and 
remain  almost  stationary  until  January.  This  large  rise  in 
September  is  a  phenomenon  which  is  not  found  by  any  other 
investigator,  and  the  fact  that  there  is  almost  no  increase 
in  three  groups  of  growing  boys  during  three  or  four  months 
from  October  to  January,  would  suggest  that  some  unusual 
influence  was  present,  such  as  a  changed  adjustment  of  the 
ergograph  or  some  internal  cause.  In  my  own  experience, 
I  know  that  merely  adjusting  a  machine  or  perhaps  oiling  it, 
makes  a  great  difference  in  the  records.  In  the  presence  of 
such  a  fact,  the  authors  should  have  studied  the  records  in 
detail  for  errors  and  considered  such  facts  in  the  conclu- 
sions concerning  the  causes  of  the  variations  found.  It 
would  seem  that  practice  effects  plus  growth  alone  would 
show  some  sort  of  increase  in  the  abilities  of  growing  boys 
during  three  or  four  months. 


24  PERIODIC    VARIATIONS    IN    EFFICIENCY 

In  regard  to  the  beneficial  effects  of  light  strength  and 
heat  strength,  the  authors  avoid  many  seeming  contradictions 
in  their  conclusions  by  clever  explanations.  In  order  to  ex- 
plain constant  growth  in  muscle  strength  they  try  to  find 
some  favorable  influence  for  nearly  all  times  of  the  year,  so 
they  hit  on  the  combination  of  light  and  heat.  From  Janu- 
ary to  May  light  is  beneficial ;  from  September  to  November 
normal  heat  is  favorable,  while  in  December  decreasing  heat 
is  unfavorable.  When  confronted  by  these  seeming  contra- 
dictions, they  explain  them  on  the  basis  of  a  movable  opti- 
mum above  or  below  which  heat  is  unfavorable.  This  is 
perhaps  one  of  the  most  important  ideas  in  the  whole  account. 
While  there  seems  to  be  no  doubt  about  the  influence  of 
sunlight  and  especially  of  changes  in  temperature  on  muscle 
strength,  it  seems  to  me  that  many  other  factors,  such  as 
food,  clothing,  and  general  manner  of  life  should  be  in- 
cluded as  causal  factors.  Though  the  authors  tried  to  elim- 
inate these  effects  as  far  as  possible  in  the  cases  of  Lehman 
and  Pedersen  by  taking  the  tests  shortly  after  rising,  they 
should  not  have  neglected  them  entirely. 

Concerning  the  effects  or  air  pressure,  a  report  of  which 
may  be  found  in  the  section  on  weather  effects,  the  facts 
seem  to  be  very  well  established.  Here,  as  in  the  case  of 
temperature,  they  suggest  the  theory  of  an  individual  opti- 
mum, above  or  below  which  atmospheric  pressure  is  injur- 
ious to  muscle  strength.  This  question  of  an  individual 
optimum  for  both  air  pressure  and  temperature  is  very  im- 
portant, and  should  be  further  investigated.  As  to  the  men- 
tal tests,  also  reported  under  weather  effects,  we  will  pass 
them  without  criticism  as  the  authors  make  no  positive  claim 
for  their  data.  Their  remarks  on  the  methods  of  studying 
mental  abilities  and  on  showing  the  results  graphically,  are 
well  and  carefully  thought  out,  and  are  well  worth  study. 

All  through  the  article  the  authors  are  very  sane  in  their 
treatment  of  results,  and  their  explanation  of  the  usefulness 


SSASONAt    PERIODICITY    IN 

bf  the  formulas  used  in  statistical  studies  is  very  valuable. 
On  the  whole,  it  is  the  most  scholarly  work  on  periodicity 
which  I  have  found,  and  must  be  taken  into  account  by  any 
who  engage  in  a  similar  study. 

5.     SEASONAL,  VARIATIONS  IN  DIURNAL  PERIODICITY. 
(KUHNES) 

(1)  Method.     Kuhnes  made  a  very  thorough  investiga- 
tion  of   diurnal   periodicity    in   physical    strength    while    a 
student  at  New  York  University,  the  results  of  which  I 
have  taken  from  an  unpublished  thesis.     In  these  tests  the 
Smedley  Dynamometer  was  used.     The  tests,  which  were 
made  mostly  on  himself,  were  taken  seven  times  daily  for 
505  "consecutive  days.    At  each  of  the  seven  test  periods,  the 
average  of  three  records  for  each  hand  was  taken,  the  six 
tests  being  taken  in  three  different  positions,  first  with  the 
left,  then  with  the  right  as  follows: 

i — each  hand  hanging  downward. 
2 — each  hand  held  vertically 
3 — each  hand  held  horizontally. 

(2)  Results.    The  principal  results  are  given  in  the  sec- 
tion  on  Diurnal   Periodicity,   but  there   are   several   state- 
ments in  his   "Summary  and   Conclusions"    which   are   of 
value  here.    They  are  as  follows : 

i — The  average  diurnal  course  of  efficiency  is  also  the 
course  of  88  per  cent,  of  the  days. 

2 — There  is  a  distinct  seasonal  periodicity  characterized 
by  a  maximum  in  December,  a  gradual  decline  through  the 
winter  with  a  minimum  in  February  and  March,  a  gradual 
rise  during  the  spring,  and  a  slightly  higher  one  in  autumn. 
There  are  marked  fluctuations  at  the  beginning  of  the  spring 
and  winter  seasons. 

3 — There  is  a  tendency  of  the  curve  of  efficiency  of  one 
year  to  follow  the  general  trend  of  the  curve  for  the  pre- 
ceding year. 

(3)  Criticism.    The  work  of  Dr.  Kuhnes  was  done  in  a 


26  PERIODIC  VARIATIONS  IN   EFFICIENCY 

very  careful  and  painstaking  maner.  The  method  of  check- 
ing was  such  as  to  eliminate  all  accidental  or  unusual  grips, 
the  average  of  forty-two  grips  being  taken  each  day,  (twen- 
ty-one with  each  hand),  and  the  method  and  procedure  were 
strictly  uniform  and  well  adapted  for  the  purpose.  The  fact 
that  only  one  person  was  tested,  a  young  man  of  scholarly 
habits  not  physically  strong  but  in  good  health,  narrows  the 
value  of  the  results  somewhat,  but  this  is  largely  outweighed 
by  the  care  and  fidelity  of  the  person  taking  the  tests;  The 
results  from  one  test  person  carefully  gathered  are  often  df 
far  more  value  than  the  results  from  a  large  number  super- 
ficially tested.  Next  to  the  investigation  of  Lehman  and 
Pedersen,  this  is  perhaps  the  most  important  investigation 
which  has  yet  been  made. 

6.     SUMMARY    OF    THE    MAIN    PROBLEMS    OF    SEASONAL 
PERIODICITY. 

At  this  point  it  may  be  well  to  summarize  the  main  prob- 
lems and  results  of  previous  investigations  of  periodicity  in 
mental  and  physical  abilities,  in  order  that  they  may  help  us 
to  a  birds-eye  view  of  the  problems  to  be  solved.  In  this 
field  we  find  a  great  diversity  of  opinion.  There  seems  to  be 
little  doubt  about  the  existence  of  seasonal  rhythms  in 
growth  in  height  and  weight,  in  blood  pressure,  and  in 
haemoglobin  content  of  the  blood,  as  well  as  in  muscle 
strength  and  in  mental  abilities.  Though  several  investiga- 
tors have  studied  the  various  aspects  of  the  problem  under  a 
great  variety  of  conditions  and  by  a  great  variety  of  methods, 
the  actual  course  of  seasonal  periodicity,  its  chief  character- 
istics, and  its  most  noticeable  effects  are  still  under  discus- 
sion, and  the  knowledge  of  its  causes  is  still  far  from  satis- 
factory or  complete. 

In  physical  strength,  Schuyten  found  for  growing  chil- 
dren a  falling  period  from  January  to  March,  a  rising  period 
from  May  to  June,  a  falling  period  from  July  to  September, 
and  a  rising  period  from  September  to  December.  Lehman 


SEASONAL    PERIODICITY    IN    ABILITIES  2? 

and  'Pedersen  found,  for  a  group  of  growing  boys  and  a 
young  girl,  a  rising  period  from  February  to  June,  a  sta- 
tionary period  from  July  to  September,  and  a  rise  to  Decem- 
ber, with  a  stationary  period  from  December  to  February. 
For  adults,  Lehman  and  Pedersen  found  a  falling  period 
from  November  to  January,  a  rising  period  from  February 
to  June,  a  falling  period  from  June  to  August,  and  a  sharp 
rise  in  September,  with  a  continued  rise  till  November. 

Kuhnes  found  a  maximum  in  November  and  December, 
a  minimum  in  Feburary  and  March,  a  gradual  rise  through 
the  spring  and  a  slightly  higher  one  in  autumn. 

These  studies  seem  to  show  that  the  rhythms  found  for 
adults  by  Lehman  and  Pedersen  and  Kuhnes  differ  from 
those  found  for  growing  young  people  by  Lehman  and  Pe- 
dersen, and  by  Schuyten,  the  curve  for  young  people  show- 
ing a  stationary  period  where  that  for  adults  shows  a  de- 
crease. The  rhythm  for  adults  seems  to  show  variations  a 
short  time  before  that  for  young  people  and  children. 

In  the  mental  tests,  Schuyten  found  a  crest  in  January, 
with  a  decrease  to  July,  and  an  increase  from  October  to 
January.  Lobsien  found  a  high  level  for  primary  memory 
around  January,  a  low  level  for  February  and  April,  and  a 
low  level  around  October,  with  a  rise  to  January.  Lehman 
and  Pedersen  found  the  best  results  in  a  memory  study, 
made  on  a  group  of  children,  in  January,  and  in  May,  with 
a  slight  drop  in  February,  June,  and  September.  Many  of 
these  authors  found  more  or  less  agreement  between  mental 
and  physical  abilities,  and  weather  conditions.  Lehman  and 
Pedersen  go  so  far  as  to  say  that  the  seasonal  variations 
found  by  them  are  a  direct  result  of  the  continued  effects  of 
temperature  and  the  strength  of  sunlight.  Other  authors 
simply  find  that  mental  and  physical  abilities  are  more  or  less 
influenced  by  the  weather.  With  these  points  in  mind,  we 
will  proceed  to  the  analysis  of  our  original  data  on  seasonal 
periodicity. 


CHAPTER  ill. 

AN  ORIGINAL  EXPERIMENTAL  STUDY  IN  SEA- 
SONAL PERIODICITY 

I.  Introduction.  During  the  school  year  from  October, 
1910,  to  June,  1911,  the  writer  conducted  an  original  experi- 
mental investigation  concerning  periodicity  as  shown  in 
mental  and  physical  tests.  These  tests  were  made  on  two 
groups  of  students  in  the  first  year  of  the  Manual  Training 
High  School  of  Washington  University,  St.  Louis,  Mo. 
The  tests  were  all  made  under  the  personal  direction  of  the 
writer  at  hours  ranging  from  9  a.  m.  to  3  p.  m.,  at  a  time 
when  the  classes  came  to  his  room  for  a  study  period.  Many 
students  took  the  tests  for  a  part  of  the  time,  but  only  ten 
(referred  to  as  the  B.  Division)  took  the  tests  daily 
throughout  the  entire  period.  Another  group  of  twenty-two 
(referred  to  as  the  A.  Division)  took  the  tests  once  each 
week  on  Friday. 

Owing  to  the  amount  of  time  consumed  by  these  tests,  it 
was  not  possible  to  give  more  than  one  physical  and  one 
mental  test  daily.  The  complete  record  of  each  of  these  tests 
will  first  be  described  separately,  after  which  the  results  will 
be  compared  with  one  another,  and  with  the  results  of  other 
investigators  of  periodicity. 

2.  PERIODICITY  AS  SHOWN  IN  PHYSICAL  TESTS. 

(1)  Purpose.    The  main  purpose  of  these  tests  was  to 
discover   any    periodic   variations    in   musicle    strength    as 
shown  by  dynamometric  tests  in  the  course  of  a  school  year. 
A  secondary  purpose  was  to  find,  if  possible,  a  verification  of 
the  work  of  Schuyten,  Lobsien,  Kuhnes,  and  Lehman  and 
'Pedersen. 

(2)  Method.     As  a  basis  for  this  investigation  a  series 
of  tests  was  made  for  strength  of  grip,  using  the  Smedley 

28 


ORIGINAL    £XPE)RI MENTAL    STUDY  2Q 

Dynamometer.  The  tests  were  made  daily  on  ten  boys,  and 
weekly  on  one  man  of  26  years  of  age  and  on  twenty-one 
boys,  all  of  the  boys  being  between  13  and  19  years  of  age. 
They  were  made  at  varying  times  during  the  day  between 
9  a.  m.  and  3  p.  m.,  except  that  none  were  made  between 
12  m.  and  I  p.  m.  All  records  were  made  under  my  personal 
direction,  and  I  was  as  careful  as  possible  to  keep  the  condi- 
tions uniform  throughout  the  investigation. 

(3)  Preliminary  Tests.    In  both  the  A.  and  B.  Divisions, 
a  series  of  preliminary  tests  was  made  for  three  days,  during 
which  time  each  subject  found  the  correct  adjustment  for 
his  hand  and  learned  to  use  his  strength  to  advantage.     It 
was  found  that  when  the  students  took  the  tests  always  in 
the  same  order,  only  two  re-adjustments  of  the  dynamometer 
were  necessary  during  the  tests  in  each  division.     In  this 
way  the  grip  length  of  each  subject  was  accommodated  and 
the  same  adjustment  was  made  each  day  for  each  pupil. 

(4)  Procedure.      In   making  the   tests  each   pupil   was 
instructed  to  hold  the  dynamometer  at  arm's  length,  with  the 
dial  face  upward.     Each  subject  was  allowed  three  trials, 
taken  alternately  for  each  hand,  only  the  highest  record  for 
each  hand  being  recorded.    This  allowed  an  interval  of  about 
30  seconds  between  any  two  records  for  the  same  hand,  so 
that   the   hand   recovered    from   the   effects    of   any   strain 
before  the  next  grip  was  taken.    The  subjects  entered  into 
the  plan  with  earnestness  and  every  one  did  his  best,  so  far 
as  the  writer  could  discover,  to  keep  the  external  conditions 
uniform. 

(5)  Results.     In  checking  the  results,  the  averages  for 
each  day  and  for  each  week  were  computed  for  each  group, 
as  was  also  the  average  of  each  pupil  in  the  B.  Div.  for 
each  week.     When  a  pupil  was  absent,  it  was  found  neces- 
sary to  count  him  in  making  up  the  daily  averages,  at  his 
average  made  during  the  other   days  of  the   week.     If  a 
pupil  was  absent  for  a  full  week  at  a  time  he  was  counted 


1- 

OS 

5 

15  ^ 

c8 

CMH 

O 

N  CJ        t>  10        <N  rH 

rH 

**    $2    °°"S 

•g 

rHCM 
r4»- 

rH  rH 

1 

«"?t-        lOb-        OiOO 

«DN      cod      iciid 
coco      •*•*      coco 

rfj 

t 

d  o 

I 

•"*  fO        15  1O        rj(  Tt" 

<! 

rHrH 

IP 

CO        rH  CM        CO  ^ 

* 

t- 

p- 

0  CD        ^  r^        ^  rH 

I 

»-» 

OrH 
rH  rH 

•*CO        IOIO        Tjtrji 

9 

10  Oi        (N  <N        t-  CT) 

>» 

rHM 

rH  T- 
rH  rH 

M 

i- 

7 

3 
>-i 

W  O>        Oi  t>        t1^  ift 
^CO        1010        Tji^J 

efl 
S 

Q 

. 

t 
t 

< 

l^(M 

do 

rH  rH 

| 
^ 
o 

m 

§ 

<N  OS        CO  1C5        ^1  ^ 

—  ::      10  10      —  — 

r-i 
L- 

w 

i! 

C01O        rH  CO               -^ 

s.^ 

> 

A 

rH  CO        CO  ^        CO  ffi 

| 

t-CM 

do 

rH  rH 

;J-: 

a 

0 

r#m        1010        ^" 

^ 

PI 

•s 

L-  : 

- 

1 

• 

i 

60      e        ©t-        rH 

d  t>     rf  c4     IQ  c4 

TfOQ        10  IO        ^-^ 

£ 

dc 

^ 

(4 

-; 

5 

d 

CD  OS        rH  N        rH  CO 

d 

t-co 

1 

1 

£ 

OS  C£>         rjl  rH         T*'  rH 
COCO        IO1O         —  — 

£ 

d  d 

C, 

(4 

rHrH 

— 

M 

a 

CMi*<        U51O 

-. 

fix 

O  t-        Tt<  rH        TJ<  rH 

c 

M 

h— 

Tf  co      10  10     T^  T}< 

« 

CD« 

S 

•^ 

0 

Q 

do 

rH  rH 

ZA. 

- 

f 

1 

03        05t-        COrH 

oiid      CMOS      eo  d 

COCO        1O-*        •<*  rj< 

> 

CO 

„ 

^ 

1 

dd 

rH  rH 

2 

-: 

M 

^2 

I 

ooi-         Ti<     COT«« 

t^TJH         OCD        r-icC 
CO  CO        IO  Tj<        ^  CO 

NrH 

1 

CO  t-        IO  t-        IO  CO 

1 

doi 

rH 

0 

cd  04      cc  CM      os  in 

COCO         •<*  Tt*         COCO 

O 

z 

as 

1 

01      2          ?j 

> 

<OQ 

.; 

<2G      =  £ 

f 

a 



ORIGINAL,  EXPERIMENTAL,  STUDY  31 

each  day  at  his  average  for  the  preceding  week.  In  this 
way  the  absent  pupils  could  not  affect  the  averages,  while 
if  a  pupil  whose  record  was  either  above  or  below  the  class 
average  was  omitted  from  the  records  for  one  day,  his  ab- 
sence might  affect  the  class  average  very  decidedly.  The 
record  of  any  pupil  who  was  absent  for  two  full  weeks  at  a 
time  was  excluded  in  making  up  the  records. 

The  monthly  averages  of  both  the  A.  and  D.  divi- 
sions for  grip  strength  are  found  in  Table  IV.  They 
show  unmistakably  the  presence  of  a  seasonable  rhythm. 
We  find  a  gradual  increase  in  strength  of  grip  for  each 
hand  from  October  to  January,  a  slight  decrease  for  each 
harfd  in  February,  a  small  increase  in  March  followed  by  a 
continuous  increase  till  June  when  the  tests  ended. 

The  same  results  may  be  seen  in  Table  V  for  weekly 
averages.  The  variations  in  the  first  three  weeks  are 
due  to  the  fact  that  several  boys  in  each  group  gripped 
so  hard  that  they  injured  their  hands.  The  large  initial 
increase  is  also  partially  due  to  practice.  We  see,  how- 
ever, that  the  period  from  October  to  the  middle  of  Jan- 
uary, is  favorable  .  Then  comes  a  period  of  depression 
until  March,  and  a  period  of  gradual  increase  until  the  end 
of  the  tests  in  June. 

The  same  results  may  be  observed  in  Tables  VIII,  IX, 
and  X,  where,  with  two  or  three  small  exceptions,  we  find 
low  records  for  the  month  of  February  for  both  hands  at  all 
ages.  A  nineteen  and  a  twenty-six  year  old  subject  both 
agree  in  showing  a  practically  stationary  period  from  De- 
cember until  March  instead  of  a  drop  in  February,  otherwise 
they  agree  with  the  seasonal  rhythm  of  the  younger  boys. 
These  facts  seem  to  agree  with  the  results  of  other  investi- 
gators on  adults  in  showing  a  rhythm  for  adults  which  dif- 
fers slightly  from  that  of  growing  children,  showing  a  sta- 
tionary period  where  the  growing  children  show  great  flue- 


O5  01O 

00  O5 

IO05O5 

(NCN 

gjp" 

O5  t—  TH 

^  o 

~|-~ 

CNO5O 

05  t-l-H 

10 

CO  CO  iH 

1O1O 

THOOHH 

IO  IO1-1 

051OCO 

1-lCO 

10     t- 

H.CN 

f° 

00  COO 
COCOTH 

s§ 

* 

CNOO 

0510^ 

L^ 

rHCOt- 

(Nrh 

CO  00  «3 

^^ 

HJ; 

O  t-  iH 
ThCOrH 

SS 

H^ 

(NOO  O 

O510TH 

71  L-. 

IOl> 

CNrHCO 

t-  10 

—  . 

oco  o 

^   T-H 

1C 

CN  05  iH 

CO  10  T-I 

-  ::  - 

1010 

1O  10  TH 

CDO5t- 

iH 

O510CN 

CO  05  CO 

»^. 

O5  CO  O 

Tj<  TH 

*-C^C 

iH  OO  TH 

06  T^'TH 

00  00  iH 

1010 

•*!  COrH 

1O1OT-1 

e»|ao 

0005TH 

0000 

05  CO  O5 

rH0505 

HN 

00  1O  CN 
CO  OCTH 

00  O 

10  10 

"fe 

—  ::  — 

IO10TH 

e*|» 

<N05 

CN 

05lOrH 

t-T-t^ 

* 

r:  v:  r 

CO  0 

1010 

•fc 

C  t^TH 

-  ::  - 

IO»OTH 

TH  t-  00 

CNCN 

05  OC^ 

CD  TH  O5 

> 

CNO5 

10  •* 

-fe 

T-iood 

T^COrH 

CCHiO 
1O  1OTH 

05  00  TH 

CNCMCO 

r.  L-  — 

CO        C» 

> 

COCOTH 

CN  05O 

*^" 

(N  05  O 

—  r:  — 

10  H<  O 
1Q10TH 

t- 

i-^Kc 

COCO 

O5  00-* 

r  :  7  ]  — 

^-  M 

C01O  O 

THOO  O 

„  "~ 

rH  t*-  O 

10  CO  O 

CO  TH 

•" 

T*t    00   TH 

101OTH 

COCD1O 

t-ooco 

05THCD 

051000 

00  1O  0 
CO  00  TH 

oco  q 

HS 

•*  COTH 

•&  01  O 
IO1O  TH 

UH 

iH        05 

CN  t-iH 

^00  <N 

00         CO 

~H 

t--*  O 
COCO  TH 

%%* 

-fe 

OCO'TH 

T*COrH 

—  r:  - 

1O10TH 

w 

<N  OM 

CJ.O  10 

IO^CD 

t-10CD 

t>  CO  iH 
CO  COrH 

O5  •*  O 

-  -  - 

•£ 

d  cod 

HHCOTH 

•*  CN  05 
1O1O 

Ojso 

—  —   — 

O5TH 

COCOTH 

COM  00 

Hv 

t-00   T-l 

OOCOTH 

IO  CN  O5 

•N)CC 

d  t-o 

TJ-COTH 

COM  05 
1010 

c£ 

H.CNCO 

t-  IO  CN 

0500TH 

O5O5 

~£ 

10  TH  O 

CC    CO  TH 

x  —  ~ 

"K- 

05  t>TH 
CO  COT-" 

OlOrH 

TH  00 

05 

0510TH 

10^,00 

0  CO  00 

—  *  j  • 

CVH 

O5  t-  O5 

•^  TH  O5 

CO  CO 

^^ 

CO  CO 

1010 

0 

*JS 

^S| 

| 

S 

Q 

-a  || 

Q 

^ 

0 

O>1O  O5  t- 

MM 

5  co'  os'  d 
.z  ~  :-  — 

S^TH 

Mr-lTH 

05TH<N 

cL  CQ  O  rH 

00  10  rH 

^  -  r:  T- 

.^-*, 

.rj<  COCO 

Q   O.TH  00  O 

Isss 

"tn 

en 

5 

S 

<    .gOO           t- 

CQcDt-M 

odt>d 

»OM"  d 

ci 

d^10rH 

•c 

"C 

O 

0 

rg 

•d 

p 

05   Oi  05  CD  O 

^  n  CO  CO  TH 

Tj<"   T-i    O 

O 

0 

cu 

CL> 

CO       t- 

<N  "*  CD 

"d  t>  d 

•  ^H  rH  d 

,_4  •"*  "•<*  co  TH 

glO^TH 

CJ 

« 

^-t  gqooco 

O  oi  10  d 

CO  CO  TH 

*s 

H«^t 

S5S 

$,ao  t-  ao 

« 

^00  CO  iH 

g'  CD  0 
TKrH 

.k*.J 

10  t-TH 

CO  CO  iH 

CO'MOJ 

**        w, 

ORIGINAL    EXPERIMENTAL    STUDY  33 

tuations,  some  showing  an  increase  while  others  show  a  de- 
crease. 
3.     PERIODICITY  AS  SHOWN  IN  PRIMARY  MEMORY  TESTS. 

(i)  Purpose.  The  main  purpose  of  this  investigation 
was  to  discover  any  periodic  variations  in  mental  abilities  as 
shown  in  primary  memory  tests,  given  through  a  school  year. 
A  secondary  purpose  was  to  see  how  the  variations  com- 
pared with  those  found  by  other  investigators  of  mental 
periodicity,  and  how  they  compared  with  the  results  from 
the  dynamometric  tests  given  to  the  same  groups  of  students, 
on  the  same  days,  at  the  same  hours,  and  during  the  same 
school  year. 

^-(z)  Method.  As  a  basis  for  this  investigation,  a  series 
of  tests  was  made  to  discover  the  ability  of  the  two  groups 
already  referred  to  as  the  A.  and  B.  divisions  in  the  dynamo- 
metric  tests,  to  reproduce  three  series  of  four,  five,  and  six 
numbers  of  two  digits  each,  immediately  after  they  were 
read  by  the  author.  The  tests  were  given  immediately  fol- 
lowing the  dynamometric  tests.  The  group  to  be  tested  was 
seated  in  front  of  the  investigator.  At  a  given  signal  all  of 
the  students  were  requested  to  come  to  attention. 

(3)  Procedure.  A  series  of  four  numbers,  as  84-26- 
47-32,  was  read  at  the  rate  of  one  per  second.  At  the  close 
of  each  series,  the  students  were  allowed  15  seconds  to  write 
the  series  of  numbers  in  the  order  of  presentation,  on  a 
record  blank  provided  for  the  purpose.  This  blank  bore  the 
name  of  the  pupil  and  of  the  division,  the  time  of  day,  date, 
character  of  the  day,  and  the  result  of  the  dynamometric 
tests  which  had  just  been  given.  Fifteen  seconds  after  the 
four  numbers  were  written,  at  a  given  signal,  a  series  of  five 
two  place  numbers  was  read  at  the  same  rate  as  before. 
Then  after  waiting  fifteen  seconds  for  the  pupils  to  write  the 
series  of  five  numbers  on  the  record  flanks,  the  attention  sig- 
nal was  given,  followed  by  six  two  place  numbers  at  the 
same  rate  as  before.  After  the  pupils  had  written  the  series 


34  PERIODIC  VARIATIONS   IN    EFFICIENCY 

of  six  numbers,  they  were  asked  to  give  any  facts  which 
helped  or  hindered  them  in  writing  the  numbers,  on  the 
reverse  side  of  the  record  sheet.  The  time  of  day,  the  char- 
acter of  the  day  in  general  and  the  temperature  were  then 
recorded  along  with  any  interesting  introspections  of  the 
students,  after  which  the  records  were  collected.  In  esti- 
mating values,  a  number  correctly  given  in  its  proper  order 
was  counted  one  point.  A  number  rightly  given  but  in  the 
wrong  order  was  counted  one-half  point.  A  number  which 
had  one  digit  correctly  given  was  also  counted  half  a  point. 
The  total  score  that  could  be  made,  therefore,  was  15  points. 

(4)  Preliminary  Tests.     In  this  investigation,  as  in  the 
one  on  muscular  periodicity,  a  series  of  preliminary  tests 
was  given  on  three  days.     The  purpose  of  the  experiment 
was  explained  to  the  pupils,  who  entered  into  the  spirit  of 
the  investigation  with  enthusiasm.    As  in  the  dynamometric 
tests,  no  one  was  asked  to  take  the  tests  unless  he  so  desired. 
In  this  experiment,  also,  absent  students  were  counted  at 
their  average  for  the  week,  or  if  absent  for  a  whole  week,  at 
their  average  for  the  preceding  week.    Those  who  were  ab- 
sent for  more  than  two  consecutive  weeks  were  dropped  from 
the  investigation. 

(5)  Results.     In   this   investigation,   the   averages    for 
each  day,  each  week,  and  each  month,  were  computed  both 
for  the  individuals,  for  all  ages,  and  for  each  group  as  a 
whole. 

The  monthly  variations  for  primary  memory  for  both 
the  A.  and  B.  divisions  are  shown  in  Tables  III,  XI  and 
XII.  The  tables  for  the  B.  division  show  a  characteris- 
tic curve  similar  to  the  curve  for  muscular  growth,  that 
for  the  A.  division  does  not  show  the  same  characteris- 
tics. The  only  striking  similarity  is  found  in  the  depres- 
sion for  February,  a  depression  which  is  found  in  all 
the  monthly  curves  for  both  mental  and  physical  tests.  If 
we  examine  Table  XI  we  find  this  same  depression  for  all 


ORIGINAL  EXPERIMENTAL,  STUDY  35 

ages  in  February  and  March.  The  same  depression  is 
found  in  nearly  all  ages  of  the  A.  group  (Table  XII),  ex- 
cept the  two  oldest  subjects.  Here  we  find  the  depression  in 
January  and  March  instead  of  February,  as  with  the  young- 
er boys.  The  only  other  exceptions  are  two  boys,  both  very 
bright  and  very  nervous,  at  age  13-14  whose  records  were 
high  through  all  the  year.  The  high  record  for  the  A. 
division  in  November  is  due  to  an  exceptionally  high  aver- 
age of  the  two  boys  mentioned,  for  the  month.  The  high 
record  for  the  A.  division  for  May  and  June  was  due  largely 
to  the  individual  record  of  an  i8-year-old  boy.  During  that 
time  this  particular  boy  was  tmder  a  very  high  nervous 
tension.  He  was  a  part  owner  of  an  airdome  which  opened 
about  that  time,  and  he  spent  his  evenings  there  until  nearly 
midnight.  He  was  old  for  the  class  but  very  bright.  He. 
had  been  out  of  school  for  about  four  years  just  preceeding 
this  time.  His  increase  in  ability  was  therefore  due  very 
largely  to  habit  and  effects  of  practice,  and  was  phenomenal. 
He  was  very  thorough  and  painstaking,  and  his  record  shows 
what  a  year  of  conscientious  study  can  do  in  sharpening  a 
boy's  mental  ability. 

With  the  exception  of  the  two  older  students  noted  above, 
the  A.  division  consisted  of  boys  who  had  been  in  school 
continuously,  and  as  a  whole  they  showed  very  little  change 
as  a  result  of  practice.  They  were  all  taking  the  Latin 
Course.  The  B.  division  was  almost  exactly  opposite  in  com- 
position. They  were  taking  the  English  Course,  and  in  gen- 
eral were  more  mature.  Only  two  of  the  ten  had  attended 
school  continuously.  The  others  had  all  been  at  work  for  at 
least  one  term  since  graduation  from  a  grammar  school,  and 
two  had  been  out  of  school  for  three  years  preceding.  In 
the  B.  division,  therefore,  we  find  that  the  low  record  for 
October  was  quite  general.  Then  as  a  result  of  practice 
largely,  it  makes  a  very  noticeable  increase  during  the  year, 
reaching  a  higher  level  than  is  reached  by  the  A.  division. 


36  PERIODIC   VARIATIONS   IN    EFFICIENCY 

The  very  high  records  for  April,  May,  and  June,  were  due 
to  the  efforts  of  two  very  bright  boys,  both  of  whom  had  been 
out  of  school  during  the  two  years  next  preceding.  The 
rise  of  these  two  boys,  as  well  as  that  for  the  whole  B.  divi- 
sion, was  due  to  the  same  cause  as  that  of  the  nineteen-year- 
old  in  the  T.  division  mentioned  above — earnest  application. 
If  we  eliminate  these  special  cases  and  the  practice  effects,  we 
find  that  the  curve  for  the  B.  division  Memory  Tests  becomes 
more  nearly  level,  the  one  outstanding  feature  being  a 
slight  drop  sometime  in  January  and  February.  We  must 
conclude,  therefore,  that  the  curve  for  primary  memory 
shows  a  rising  tendency  with  favorable  influences  from 
October  to  January,  a  period  of  depression  for  January, 
February,  and  the  first  part  of  March,  and  a  rising  tendency 
with  favorable  influences  from  March  to  June. 

4.     COMPARISONS  OF  MENTAL  AND  PHYSICAL  SEASONAL 
PERIODICITY. 

If  we  compare  the  results  from  the  mental  and  physical 
tests  in  the  two  accounts  just  given,  they  show  certain  strik- 
ing similarities.  They  all  show  a  sharp  rise  at  the  begin- 
ning, a  regular  improvement  until  January,  a  period  of  de- 
pression from  the  middle  of  January  to  the  first  of  March, 
and  a  regular  rise  to  the  ends  of  the  tests.  While  there  are 
a  few  differences,  the  general  tendencies  outweigh  them. 
The  larger  changes  in  muscle  strength  are  undoubtedly  due 
to  a  large  extent  to  physical  growth 'and  practice  effects. 
In  Tables  IX  and  X,  we  find  that  the  greatest  increase  in 
physical  strength  was  in  boys  from  15  to  17  years  old.  W^ 
also  see  that  the  increase  for  nine  months  for  those  who  took 
the  tests  five  times  per  week  was  for  all  ages  nearly  double 
the  increase  made  by  those  who  took  the  tests  but  once  per 
week.  It  would  seem,  therefore,  that  about  one-half  of  the 
improvement  of  the  B.  division  was  the  effect  of  the  extra 
practice  received  by  that  group. 


ORIGINAL  EXPERIMENTAL  STUDY  37 

We  also  have  the  interesting  phenomena  that  at  all  ages 
except  at  16-17,  the  gain  with  the  left  hand  was  greater  than 
with  the  right,  in  one  case  being  three  times  as  great.  The 
average  gains  with  the  right  and  left  hands  for  those  who 
took  the  tests  five  times  weekly  was  12.7  Kg.^  and  14.5  Kg., 
respectively,  while  that  for  those  tested  but  once  per  week 
was  6.2  Kg.  and[  7.2  Kg.,  respectively,  for  the  same  time.  In 
no  case  was  a  continuous  gain  made  during  each  of  the  nine 
months  except  in  the  case  of  one  boy  15-16  years  old  in  the 
B.  division. 

In  the  Mental  Tests  the  effects  of  practice  and  growth 
are  very  small.  In  no  case  in  either  group  was  a  continuous 
monthly  gain  made  throughout  the  year.  With  the  exception 
Of  five  individuals,  every  boy  had  made  his  highest  record 
of  the  entire  series  of  tests  by  the  first  of  January.  The 
highest  records  in  the  entire  set  of  tests  were  made  by  five 
individuals,  two  of  the  very  bright  boys  between  the  ages  of 
13  and  14  years,  and  three  older  boys,  one  17,  one  18,  and 
one  19  years  old,  each  of  whom  had  been  out  of  school  and 
working  during  the  two  or  three  years  just  preceding. 

The  Dynamometric  tests  for  variations  in  physical  abili- 
ties seem  to  be  an  excellent  means  for  judging  the  growth 
and  development  of  physical  strength.  The  same  validity, 
however,  cannot  be  claimed  for  the  mental  tests  used  in  this 
investigation.  Records  made  by  individuals  from  day  to  day 
were  very  erratic,  and  often  seemed  to  be  without  any  ap- 
parent causes  in  spite  of  all  precautions  to  make  the  material 
and  procedure  uniform  from  day  to  day. 

The  abilities  of  this  group  in  primary  memory  were  prac- 
tically fixed  before  the  tests  began,  and  in  only  a  few  cases 
were  any  large  practice  effects  noticeable.  One  of  the  great- 
est difficulties  in  mental  tests  is  that  many  boys  become  con- 
fused when  engaged  in  taking  them.  Among  the  ten  boys 
in  the  B.  division  who  took  the  tests  daily,  five  could 
usually  be  depended  upon  to  make  good  scores.  The  other 


38.  PERIODIC   VARIATIONS   IN    EFFICIENCY 

five  were  very  nervous  and  easily  became  confused,  making 
often  very  low  records.  I  have  taken  the  individual  records 
of  each  boy,  and  by  comparing  them  with  the  records  of  tem- 
perature, humidity,  etc.,  sought  to  discover  causes.  In  most 
cases  the  results  of  such  comparisons  are  contradictory  or 
baffling.  But  this  is  a  condition  that  every  one  who  gives 
mental  tests  must  expect  to  meet,  and  in  order  to  meet  it,  the 
investigators  depend  on  statistics. 

Every  science  grows  by  improvement  in  its  methods,  and 
while  the  method  used  in  the  mental  tests  is  far  from  perfect, 
it  is  about  as  reliable  as  any  yet  devised.  The  memory  re- 
sults are  valuable  because  this  is  one  of  the  most  exhaustive 
tests  ever  made,  and  they  are  doubly  valuable  for  purposes  of 
comparison  with  the  records  of  the  physical  tests,  given  to 
the  same  groups  at  the  same  time  each  day  for  so  long  a 
period.  So  far  as  I  have  been  able  to  discover,  it  is  the  only 
investigation  which  combines  the  results  of  mental  and 
physical  tests  on  a  homogeneous  group  for  so  long  a  time. 

A  comparison  of  the  tables  shows  quite  conclusively 
that  the  same  set  of  causes  operate,  to  a  certain  extent 
at  least,  in  controlling  both  mental  and  physical  abilities 
through  a  relationship  as  yet  unknown  in  detail.  This 
is  especially  seen  in  the  period  of  depression  in  January  and 
February,  a  period  which  all  investigators  have  found, 
though  the  exact  time  it  occurs  differs  in  individuals,  and  in 
all  probability  differs  under  varying  weather  conditions.  The 
school  building  where  the  boys  spent  their  time  was  almost 
ideal  as  to  light,  space,  ventilation,  temperature,  and  humid- 
ity, and  these  favorable  surroundings  tended  to  cause  both 
mental  and  physical  energy  to  grow  beyond  the  time  where 
a  pause  usually  takes  place. 

The  individual  records  show  that  the  period  of  depression 
in  muscle  strength  begins  anywhere  between  the  middle  of 
December  and  the  middle  of  January,  arid  lasts  from  3  to 
10  weeks.  In  some  subjects  its  effects  are  overcome  by  the 


ORIGINAL    £XP£RI MENTAL    STUDY  39 

middle  of  February,  in  others  it  lasts  until  sometime  in 
March,  and  in  one  case  of  a  1 7-year-old  boy,  it  lasted  from 
February  to  May.  In  general  the  boys  of  low  vitality  in 
the  early  winter,  are  the  ones  who  show  the  depression  first. 
Several  boys  showed  more  than  one  period  of  depression,  but 
the  only  period  of  depression  shown  by  every  individual 
tested  was  the  one  which  began  some  time  between  the  mid- 
dle of  December  and  the  middle  of  January,  and  lasted  from 
three  to  ten  weeks,  varying  with  individuals. 

While  the  averages  for  the  memory  tests  show  the  same 
general  tendencies,  the  depression  tends  to  appear  slightly 
earlier  in  some  cases  and  slightly  later  in  others.  The  rec- 
ords from  day  to  day  vary  so  much,  due  to  accidental  causes, 
that  it  is  sometimes  difficult  to  see  the  depressions  in  the 
weekly  averages,  but  the  individual  monthly  averages  bring 
out  the  depression  referred  to  in  the  preceeding  sentence  in 
almost  every  individual  tested. 

These  results  tend  to  confirm  the  results  of  Kuhnes  and 
Lehman  and  Pedersen  on  one  hand,  and  those  of  Schuyten 
and  Lehman  and  Pedersen  on  the  other.  They  show  that  in 
periodicity,  the  time  and  extent  of  the  period  of  depression 
about  the  beginning  of  the  year  is  different  for  adults  and 
for  youths.  They  also  tend  to  clear  up  the  conflicting  results 
of  other  investigators  who  found  periods  of  depression  all  the 
way  from  November  to  March,  by  showing  that  these  are 
simply  individual  variations  of  a  more  or  less  universal 
phenomenon. 

They  tend  to  dispute  the  idea  that  physical  and  mental 
abilities  go  by  contraries  as  do  growth  in  height  and  weight. 
Finally,  they  give  added  validity  to  the  idea  of  a  seasonal 
growth  rhythm,  a  cosmic  rhythm,  which,  allowing  for  various 
individual  differences  in  adaptation,  affects  all  individuals 
profoundly,  and  is  manifested  in  a  multitude  of  ways  in 
human  life. 


TABLE:  vin 


TABLE  vin,  B  DIVISION 

Hu-  %  Char. 
Avg.  mid-Sun  of 

WEEKLY  AVERAGES 

Mo.  Tern. 

ity  shine  dav 

Tic  r 

R 

L 

M 

4's 

5's 

6'f 

Oct.  10 

58 

•93 

100 

Cl 

2  P.M. 

43 

40 

10.3 

4 

3.1 

3.2 

11 

64 

91 

60 

Cl 

10  A. 

43.3 

39.5 

8.3 

3.3 

2.5 

2.5 

12 

67 

91 

77 

•  Cl 

11  A. 

46.1 

41 

8.2 

3.1 

2.8 

W.  3 

13 

68 

57 

58 

PC 

1  P. 

46.2 

42.9 

11 

3.7 

4.1 

3.2 

14 

70 

69 

60 

PC. 

1  P. 

44.7 

42.4 

10.5 

4 

3,5 

3 

17 

74 

53 

87 

Cl 

2.  P. 

44.9 

42 

8.8 

3.3 

3.1 

2.4 

18 

74 

82 

100 

Cl 

11  A. 

46.2 

41.3 

9 

2.8 

3.2 

3 

19 

65 

80 

76 

Cl 

1  P. 

45.9 

43.3 

9.4 

3.4- 

3.5 

2.5 

20 

47 

86 

0 

c 

9  A. 

43.7 

42.3 

9.8 

3.4 

3.4 

3 

21 

44 

94 

0 

c 

1  P. 

42.6 

43 

9.4 

3.5 

3.1 

3.5 

24 

60 

51 

69 

Cl 

9  A. 

45.5 

42.4 

10 

3.7 

2.9 

3.4 

25 

58 

24 

81 

Cl 

1  P. 

50.5 

44.3 

9.3 

3.2 

3.4 

2.7 

26 

67 

64 

90 

Cl 

9  A. 

47.2 

45.3 

9.5 

2.5 

3.8 

3.2 

27 

46 

36 

56 

PC 

1  P. 

47.7 

43.9 

9 

3.8 

2.3 

2.9 

28 

34 

55 

0 

c 

1  P. 

49.6 

42.5 

8.8 

3.5 

2.6 

2.7 

31 

59 

44 

75 

Cl 

10  A. 

49.6 

44 

11.7 

3.8 

4.3 

3.6 

Nov.  1 

54 

68 

12 

c 

1  P. 

48.7 

47.4 

10.5 

3.6 

3.3 

3.6 

2 

40 

63 

79 

Cl 

9  A. 

47.9 

43.5 

10.3 

3.9 

3.3 

3.1 

3 

36 

56 

100 

Cl 

9  A. 

47.8 

44.2 

9.7 

3.2 

3.3 

3.2 

4 

38 

63 

0 

c 

9  A. 

46.6 

43.7 

10.8 

4 

3.5 

3.3 

7 

54 

65 

100 

Cl 

9  A. 

49.2 

45.9 

10.1 

3.5 

3.7 

2.9 

8 

51 

80 

87 

Cl 

10  A. 

48.1 

45.5 

11.6 

3.9 

4.2 

3.5 

9 

60 

73 

91 

Cl 

9  A. 

50.1 

46.3 

10.9 

3.8- 

3 

4.1 

10 

40 

87 

59 

PC 

9  A. 

49.6 

44.8 

9.9 

3.8 

3.2 

2.9 

11 

36 

77 

98 

Cl 

9  A. 

49 

46.6 

10 

3.8 

3.1 

3.1 

14 

40 

54 

49 

c 

2  P. 

51.2 

46.1 

11 

3.3 

3.3 

4.4 

15 

34 

69 

0 

c 

2  P. 

49.3 

44.7 

11.3 

3.8 

3.8 

3.7 

16 

34 

85 

46 

PC 

2  P. 

50.7 

47.5 

10.7 

4 

3.1 

3.6 

17 

33 

70 

0 

c 

2  P. 

50.5 

47.3 

10.9 

3.6 

3.6 

3.7 

18 

40 

60 

20 

c 

2  P. 

49 

47.9 

9.5 

3.5 

2.9 

3.1 

21 

44 

72 

7 

PC 

2  P. 

50.1 

48.4 

10.2 

3.3 

3.3 

3.6 

22 

40 

87 

100 

Cl 

1  P. 

50 

47.9 

11.6 

3.9 

3.8 

3.9 

23 

52 

61 

100 

Cl 

11  A. 

51.4 

49.4 

9.2 

3.7 

2.8 

2.7 

24 

Thanksgiving 

Day 

25 

49 

49 

82 

Cl 

2  P. 

51.2 

48.1 

10.4 

3.7 

3.3 

3.4 

28 

32 

72 

95 

Cl 

2  P. 

52.6 

48.6 

8.9 

3.6 

2.8 

2.5 

29 

32 

84 

8 

PC 

2  P. 

51.8 

48.1 

10.7 

3.8 

3.5 

3.4 

30 

26 

59 

100 

Cl 

11  A. 

52.2 

49.4 

10.9 

3.8 

3.3 

3.8 

Dec.  1 

23 

64 

0 

c 

2  P. 

53 

49.4 

9.9 

3 

3.4 

3.5 

2 

26 

52 

23 

c 

2  P. 

52 

50.1 

11 

3.9 

3.1 

4 

5 

30 

61 

0 

c 

2  P. 

52.1 

49.5 

10.7 

3.5 

3.8 

3.4 

6 

26 

49 

0 

c 

1  P. 

53.5 

49.3 

10.9 

3.8 

4 

3.1 

7 

28 

60 

76 

Cl 

2  P. 

50.3 

48.7 

10.2 

3.3 

3 

3.9 

8 

30 

50 

39 

Cl 

1  P. 

52.1 

49.4 

9.2 

3.4 

2.7 

3.1 

9 

34 

64 

4 

c 

2  P. 

51.3 

48.5 

1O.8 

3.6 

3.4 

3.8 

TABLE:  vm  (Con'd) 


TABLE  vm,  B  DIVISION 

Hu-  %  Char. 
Avg.  mid-  Sun  of 

WEEKLY  AVERAGES 

Mo.  Tern. 

ity  shine  day 

Hour 

R 

L 

M 

4's 

5's 

6's 

12 

21 

52 

33 

PC 

2  P. 

nt.9 

53.6 

11.1 

4 

3.2 

3.9 

13 

21 

50 

70 

Cl 

2  P. 

52.4 

46.7 

11 

3.6 

3.7 

3.7 

14 

34 

30 

100 

Cl 

2  P. 

51.7 

49.2 

11.2 

3.3 

3.7 

4.2 

15 

38 

51 

84 

Cl 

2  P. 

51.4 

4'9.6 

9.7 

3.9 

2.8 

3 

16 

36 

58 

100 

Cl 

2  P. 

52.3 

47.7 

10.3 

3.8 

3.2 

3.3 

19 

39 

48 

38 

c 

2  P. 

53.4 

48.9 

11.6 

3.6 

3.7 

4.3 

20 

28 

69 

79 

Cl 

10  A. 

54.3 

49.9 

11.2 

3.6 

3.6 

4 

21 

30 

59 

69 

Cl 

1  P. 

52.8 

49.8 

11.1 

3.5 

4.6 

3 

22 

36 

95 

0 

c 

2  P. 

52.9 

50.3 

11.5 

3.8 

3.9 

3.8 

23 

30 

62 

66 

Cl 

1  P. 

55.3 

51 

11.9 

4 

4.2 

3.7 

Jan.  9 

32 

47 

83 

Cl 

2  P. 

53.6 

51.2 

12.1 

3.6 

3.9 

4.6 

r  v  10 

46 

69 

92 

PC 

2  P. 

53.8 

52.1 

10 

3.6 

3 

3.4 

11 

51 

81 

38 

c 

2  P. 

54 

51.2 

9.9 

3.5 

3.5 

2.9 

12 

30 

83 

0 

c 

2  P. 

54.5 

50.5 

10.3 

3.7 

3.6 

3 

13 
*   " 

36 

100 

0 

c 

2  P. 

53.8 

50.9 

10.5 

3.7 

3.6 

3.2 

16 

25 

72 

0 

c 

2  P. 

53.9 

52.4 

10.4 

3.8 

3.6 

3 

17 

27 

100 

0 

c 

2  P. 

55.5 

51 

10.6 

3.7 

3.4 

3.5 

18 

26 

93 

0 

c 

2  P. 

55 

52.5 

11.4 

3.8 

3.7 

3.9 

19 

37 

96 

85 

Cl 

2  P. 

55 

50.2 

10.5 

3.5 

3.5 

3.5 

20 

44 

87 

6 

c 

2  P. 

55.8 

52.2 

11.6 

3.3 

3.6 

4.7 

23 

34 

61 

68 

re 

2  P. 

52.9 

49 

9.8 

3.8 

3.1 

2.9 

24 

40 

60 

4'9- 

c 

2  P. 

54.5 

•  51.7 

10.4 

4 

2.5 

3.9 

25 

47 

88 

0 

c 

2  P. 

54.9 

52.4 

10.9 

4 

3.5 

3.4 

26 

58 

76 

44 

c 

2  P. 

53.9 

51.5 

10.5 

3.9 

3.6 

3 

27 

49 

84 

9 

c 

2  P. 

55.9 

52.2 

10.8 

4 

3.9 

2.9 

30 

34 

55 

76 

Cl 

2  P. 

53.3 

50.7 

10.7 

4 

2.9 

3.8 

31 

48 

66 

73 

PC 

2  P. 

53.8 

50.9 

10.2 

3.9 

3.2 

3.1 

Feb.  1 

64 

44 

100 

Cl 

2  P. 

54.6 

49/9 

11.2 

3.8 

3.5 

3.9 

2 

36 

73 

100 

Cl 

2  P. 

53.9 

50.5 

10.8 

3.2 

3.2 

4.4 

3 

36 

81 

16 

c 

2  P. 

53.9 

50.5 

11 

4 

3.5 

3.5 

6 

35 

89 

0 

c 

2  P. 

54.1 

49.8 

10 

3.1 

3.2 

3.7 

7 

34 

82 

2 

c 

2  P. 

53.5 

49.9 

10.2 

3.4 

3.2 

3.6 

8 

33 

67 

73 

PC 

2  P. 

54.1 

51.3 

10.2 

3.2 

3.5 

3.5 

9 

35 

78 

100 

Cl 

2  P. 

54.3 

50.4 

9.8 

3.3 

3.1 

3.4 

10 

30 

64 

100 

Cl 

2  P. 

54.4 

51.8 

10.1 

3.6 

3.4 

3.1 

13 

48 

90 

38 

c 

2  P. 

53.5 

50.8 

9.5 

3.4 

3.3 

2.8 

14 

50 

67 

54 

Ps 

2  P. 

54.7 

49.9 

9.5 

3.1 

2.7 

3.7 

15 

54 

48 

100 

Cl 

2  P. 

55.3 

51 

9.6 

3.6 

3.5 

2.5 

16 

66 

77 

45 

PC 

2  P. 

55.3 

52.5 

10.7 

3.7 

3.7 

3.3 

17 

60 

82 

89 

Cl 

2  P. 

54.9 

52.3 

9.7 

3.4 

3.3 

3 

20 

23 

76 

42 

PC 

2  P. 

54.5 

51.5 

10 

4 

3.1 

2.9 

21 

20 

83 

75 

PC 

2  P. 

54.7 

51.5 

9.8 

3.9 

2.5 

3.4 

22 

Washin 

ton's  Birthday 

23 

30 

89 

61 

Cl 

2  P. 

53.3 

52.3 

10.8 

4 

3.6 

3.2 

24 

36 

80 

100 

Cl 

2  P. 

53.7 

53.1 

9.2 

3.1 

3.1 

3 

TABLE  VIII    (COn't) 


TABLE  vm,   B   DIVISION 


WEEKLY   AVERAGES 


Hu-   %  Char. 
Avg,.  mid-  Sun  of 


Mo.  Tern. 

ity  shine  day 

Honr 

B 

L 

M 

4's 

5's 

6's 

27 

34 

77 

100 

Cl 

2  P. 

53.9 

51.2 

9.8 

3.5 

3.3 

3 

28 

28 

100 

0 

C 

2  P. 

53.3 

51.4 

10.1 

3.4 

3.6 

3.1 

Mch.  1 

3K> 

75 

25 

C 

2  P. 

52.5 

51.4 

10.3 

3.1 

3.2 

3.3 

2 

36 

84 

100 

Cl 

2  P. 

53 

51.3 

10.2 

3.4 

3.2 

3.6 

3 

49 

68 

100 

Cl 

2  P. 

55 

52.8 

10.1 

3.9 

3 

3.2 

6 

52 

74 

32 

PC 

2  P. 

54.4 

51.9 

10.2 

3.8 

3.1 

3.3 

7 

43 

79 

0 

C 

2  P. 

54.3 

52.7 

10.9 

3.6 

3 

4.3 

8 

48 

59 

66 

Cl 

2  P. 

55 

52.5 

9.2 

4 

2.4 

2.8 

9 

60 

59 

79 

Cl 

2  P. 

55.1 

52.3 

9.8 

3.7 

2.9 

3.2 

10 

56 

42 

52 

PC 

2  P. 

54.9 

52.9 

11 

3.7 

3.3 

4 

13 

40 

48 

90 

Cl 

2  P. 

54.3 

52.3 

11 

3.9 

3.6 

3.5 

14 

46 

31 

97 

Cl 

2  P. 

54.4 

52.5 

10.8 

3.9 

3.4 

3.5 

15 

36 

51 

96 

Cl 

2  P. 

54.5 

53 

10.5 

3.4 

2.8 

4.3 

16 

30 

36 

85 

PC 

2  P. 

55.7 

54.1 

10.6 

3.9 

3.3 

3.4 

17 

50 

97 

39 

PC 

2  P. 

55.1 

52.9 

•9.1 

3 

3.7 

2.4 

20 

59 

27 

100 

Cl 

2  P. 

56.3 

53.3 

10.4 

3.7 

3.1 

3.6 

21 

64 

32 

84 

Cl 

2  P. 

54.3 

53.5 

11.8 

4 

3.8 

4 

22 

54 

28 

67 

C 

2  P. 

54.9 

53.5 

10.9 

3.8 

2.9 

4.2 

23 

42 

39 

100 

Cl 

2  P. 

55.4 

52.9 

12 

3.9 

3.9 

4.2 

24 

43 

32 

100 

Cl 

-2  P. 

53.8 

51.4 

10.7 

3.7 

3.3 

3.7 

27 

41 

42 

90 

Cl 

2  P. 

55.5 

52.8 

11.6 

4 

3.9 

3.7 

28 

50 

36 

81 

Cl 

2  P. 

55.3 

53.4 

10.1 

3.3 

2.8 

4 

29 

45 

84 

58 

PC 

2  P. 

55.8 

53.5 

10 

3.8 

3 

3.2 

30 

37 

45 

59 

PC 

2  P. 

54.9 

54 

9.7 

3 

3.1 

3.6 

31 

38 

52 

6 

Cl 

2  P. 

55.2 

52.7 

11.0 

3.8 

3.8 

3.4 

Apr.  3 

44 

91 

4 

Cl 

2  P. 

54.6 

53.8 

11.5 

3.8 

3.6 

4.1 

4 

58 

81 

30 

Cl 

2  P. 

54.6 

54.6 

12.2 

3.6 

3.9 

4.7 

5 

48 

63 

29 

Cl 

2  P. 

56.2 

53.2 

10.5 

3.5 

3 

4 

6 

58 

77 

47 

Cl 

2  P. 

56.1 

54.8 

11.2 

4 

4 

3.2 

7 

39 

50 

29 

Cl 

2  P. 

56.2 

53.2 

10.9 

4 

3.4 

3.5 

10 

50 

44 

75 

PC 

2  P. 

55.7 

55.1 

11.8 

3.8 

4.3 

3.7 

11 

52 

93 

0 

C 

2  P. 

56.7 

53.9 

9.8 

2.9 

3 

3.9 

12 

60 

61 

63 

PC 

2  P. 

55.8 

53.6 

11.1 

3.7 

3.2 

4.2 

13 

60 

94 

34 

C 

2  P. 

55.9 

54 

11.5 

3.9 

3.6 

4 

14 

49 

44 

73 

Cl 

2  P. 

55.9 

54 

11.5 

3.8 

3.5 

4.2 

17 

64 

30 

84 

Cl 

2  P. 

54.4 

52.2 

11.7 

3.6 

3.9 

4.2 

18 

59 

86 

7 

C 

2  P. 

57.8 

55.3 

10.0 

3.3 

3 

3.7 

19 

58 

60 

61 

PC 

2  P. 

57.8 

54.5 

9.7 

3.3 

3 

3.4 

20 

60 

50 

50 

PC 

2  P. 

56.8 

54.1 

10.7 

3.5 

3.4 

3.8 

21 

60 

37 

74 

Cl 

2  P. 

56 

54.1 

10.3 

3.4 

3.2 

3.7 

24 

50 

43 

99 

Cl 

2  P. 

56.3 

53.5 

10.4 

3.7 

3.1 

3.6 

25 

54 

38 

100 

Cl 

2  P. 

56.4 

55 

12.7 

4 

3.7 

5 

26 

62 

36 

67 

PC 

2  P. 

56.4 

55.8 

11.7 

4 

2.7 

5 

27 

56 

83 

0 

C 

2  P. 

58.9 

55.8 

10.2 

3.7 

3 

3.5 

28 

64 

66 

31 

PC 

2  P. 

57 

54.8 

11.2 

3.8 

3.1 

4.3 

TABLE  viii  (Con'd) 


43 


TA] 

3LE 

Avg. 

vin,  B  DIVISION              WEEK 

Hu-   %   Char. 
mid-Sun    of 

LY  AVERAGES 

Mo.    r 

Fern. 

itvs 

bine  < 

lav 

j_T~  

R 

I, 

M 

4.'* 

5's 

6's 

May    1 

51 

96 

3 

C 

2  P. 

57 

54.3 

12.3 

4 

3.9 

4.4 

2 

48 

42 

100 

Cl 

2   P. 

57.7 

53.7 

11.9 

3.4 

3.9 

4.6 

3 

49 

40 

7 

C 

2  P. 

58.9 

57.3 

10.8 

4 

3.5 

3.3 

4 

54 

35 

100 

Cl 

2P. 

59.2 

54.3 

11.2 

3.9 

3.4 

4.9 

5 

55 

32 

100 

Cl 

2  P. 

58.7 

55.8 

11.5 

3.7 

3.7 

4.1 

8 

71 

50 

100 

Cl 

2  P. 

57.1 

55.4 

10.9 

3.9 

3.1 

3.9 

9 

78 

35 

99 

Cl 

2P. 

59.0 

55.9 

11.7 

3.3 

4.4 

3.9 

10 

76 

47 

100 

Cl 

2   P. 

58.6 

54.6 

10.5 

3.7 

3.8 

3 

11 

70 

36 

80 

PC 

2  P. 

59.7 

55.6 

11.0 

3.8 

4.1 

3.1 

12 

72 

27 

89 

PC 

2  P. 

58.6 

55.4 

11.1 

3.7 

4 

3.4 

15 

76 

43 

92 

Cl 

2  P. 

60.1 

56.8 

10.8 

3.9 

3.8 

3.1 

16 

78 

52 

78 

01 

2   P. 

59.9 

54.5 

10.6 

3.7 

3.5 

3.4 

.-17 

80 

5.3 

100 

Cl 

2  P. 

58.7 

53.6 

10.5 

3.7 

3.3 

3.5 

18. 

81 

47 

90 

Cl 

2  P. 

58.4 

55.1 

11.6 

3.5 

3.8 

4.3 

19 

78 

53 

100 

Cl 

2   P. 

58.4 

54.3 

11.5 

3.9 

4 

3.6 

22 

71 

40 

86 

Cl 

2   P. 

58.9 

55 

11.3 

4 

4 

3.3 

23 

70 

37 

100 

Cl 

2  P. 

59.5 

55.4 

11.5 

3.9 

3.8 

3.3 

24 

78 

29 

100 

Cl 

2  P. 

59.8 

55.6 

11.2 

3.2 

3.9 

4.1 

25 

82 

38 

100 

Cl 

2   P. 

58.4 

56 

11.1 

3.5 

4.2 

3.4 

26 

83 

41 

98 

Cl 

2  P. 

57.8 

54.6 

11.4 

3.6 

4.1 

3.7 

29 

77 

53 

84 

Cl 

2  P. 

58.6 

56.4 

10.5 

3.5 

3.6 

3.4 

30 

78 

67 

82 

PC 

2  P. 

59.6 

57.8 

11 

3.8 

4.1 

3.1 

31 

74 

53 

78 

Cl 

2  P. 

59 

57.7 

11.2 

3.6 

4 

3.6 

June  1 

72 

54 

87 

Po 

2  P. 

59.3 

57.7 

11.3 

3.7 

3.8 

3.8 

2 

76 

49 

82 

PC 

2  P. 

59.7 

57.3 

11 

3.5 

3.9 

3.6 

O3  »Q  CO  IO  ^p,'"*  t~.t°.  *~l  ^ 
CO  N  Old  00  IO  CD  •«*  ^  rH 
„*  r*  -*rj<  IQ10  IOIO  IOIO 


t-oo      tot- 

~  L-'      cr  ?i 


10  »0 

^ 


lOCO        t-rH        t-  OOiO        OlrH 

10-*        •<*<  •*        COCO       IOIQ        1010 


CN  t>-00        03J3        O3CM        "*CO 

d  10      id co      d  t-      id  06      CD-* 

IO  ^        TJ<  rji        CO  IO        IO  IO        IOIO 


^        ^i/i— i        rHrH        1>»O3  COt~ 

06  cd      id  co      06  id      10  Tt<      Ti*  c4 

•*•*        IOIO        1010        IOIO 


00  COCO        iHCM 


O303        00»        CON        N-^  ^ 

O 


0103        01CO        03t- 
1010        IOIO        IO-* 


CO 

COCO        COrH        IO  IO  IO  •* 

—  ::        ~-  ".        ir.  L-        L-  L-        i?.  ^ 


^0> 
03-*        O3IO        t-rjH        I>  X        10  t- 


^  CM  -.  10  CNJ 


S         t« 


05  »> 

ION 

05  CD 

rH05 

NN 

0 

r^OO 

»oco 

t-  t~ 

t-IrH 

rH  CO        CO  •HH        CO  t> 
rH 

to 

IO  00 

CD 

N 

CO  10 

05  N        CO  c<|              00 

5 

cod 
coco 

CO  05 
CO  N 

CO  0 

53 

rHCO        N^         O  CD 

•^  rH        CO  ^        rH  CO 

£ 

00 

rH  CO 

rH 

O5  O 

CO  t> 

o 

HH 

05  CD 
N  N 

05  10 

coco 

co  d 

0  10        rH  CO        co  c<i 
rJH  CO         rH  **         COCO 

50 

05  »0 

0510 

05 

CO  CO 

IO  05 

5 

coco 

CO  CO 

CO  CO 

ri  IO 
10  rH 

^H  00        rH  t~        N  O5 
•^  rH         rH  ^         rH  CO 

CD 

iqio 

IO 

05  t- 

COCO 

>OO5 

P 

rH  N 

CD  CM 

rH  IO 

rH  00        N  0        N  05 

OJO5 

CO  CO 
0500 

rH  rH 
CO  CO 

CO  00 

N  t-                           N  rH 

cS 

rH  CM 

rH  rH 

ION 

rH  rH 

rH  CO        CO  CO        (N  05 

§ 

coco 

•COCO 

10  rH 

rHrH        rH   -          rHCO 

t~ 

00  N 

N 

oo  oi 

CO                               COIO 

Pi 

^ 

rH  O 

10  CO 

05  CM' 

ON        N  rH        rH  00 

<i 

CO  CO 
10  »0. 

CO  CO 
CO  CO 

O5 

rH  IO 

IO  00        00              00 

O 

rH  N* 

COO5 

rH  rH 

00  rH 

ON        rH  CO        O  t- 

§ 

coco 

CON 

rHrH 

rHrH         rHrH         rHCO 

N 

COOi 

00  rH 

t>  CO 

CO        CO05 

3 

coo 

NO5 

N  O 

COrH 

ON         CO  CO        05*  CD 

> 

h 

CO  CO 

CO  N 

Q 

CO  CO 

CO  05 

O5  CO 

rHrH 

a, 

§ 

rH  rH 

N  05 

N  05 

l>rH 

ON         CO  CO        Oc- 

-n 

1-3 

CO  N 

rH  CO 

C 

CO 

t> 

rH  CO 

IO  rH 

00 

^i 

| 

coo 

N  CO 

O  00 

lOr-i 

rH  rH         rH  CO         O5  IO 

& 

Q 

CO  CO 

CO  N 

rH  CO 

rH  rH         rH  rH         CO  CO 

B 

V 

c 

CO 

• 

00 

rH  ^ 

N  IO 

10  CO 

O5  t-        00  t- 

o 

N  t- 

CON 

rH  t- 

CON 

O  t- 

rH  O 

NO         CO  CO         t>  rH* 
rH  rH        rH  rH        CO  CO 

>< 

^j 

00 

rH  CO 

rH 

O5rH 

CO  t- 

g 

S 

016 

CON 

05  CD 
(NN 

C^  10 
COCO 

CO  O 

rH  IO        rH  CO        CO  N 

rH  CO        rH  rH        CO  CO 

I 

"* 

"!? 

'f 

CO 

P4>4        CdrH*        P4|_I 

& 

-23 

2% 

-2S 

o^ 

Jjjj 

j 

2 

£ 

s 

< 

CO        CO        CO        rH 


^  10        T-H        CO         05  t> 

pOrHOOCOOO 


>>          <N        r-         10        O5        CD  r- 


^  Ci        TJ<        CO        OJ  00        t- 

<1  rH         rH        rH         rH  rH 


IO        U5        (M         00        CO 


00        CO        CD        CO 


h 
b 


<N  10        10 

' 


rH        f-        CO         CO        CO         rH 


O\         <r>         ^H         --i 


Oio    O^o    Ot 

-',-l—  ^-i-« 
-<fr  VO  VO 


CHAPTER    IV. 

DIURNAL  VARIATIONS  IN  EFFICIENCY 

I.  Introduction.  The  question  of  diurnal  variations  in 
mental  and  physical  abilities  has  received  a  great  deal  of  at- 
tention during  the  past  few  years,  and  since  it  is  involved 
in  the  larger  question  of  seasonal  periodicity,  a  brief  survey 
of  the  progress  in  this  field  will  be  presented  and  the  results 
of  others  compared  with  those  of  my  own  original  investiga- 
tions. The  results  in  this  field  show,  with  minor  differences, 
a  substantial  agreement.  Several  years  ago,  Lombard28, 
in  a  series  of  experiments  using  his  modification  of  Mosso's 
Ergograph,  found  the  most  favorable  periods  of  the  day  to  be 
between  10  and  n  a.  m.  and  10  and  up.  m.,  and  the  poorest 
between  3  and  4  a.  m.  and  3  and  4  p.  m.  He  also  noted  a  rise 
in  ability  about  2  p.  m.,  which  entirely  disappeared  between 
3  and  4  p.  m. 

Patrice32,  in  testing  the  strength  of  himslf  and  one  other 
with  Mosso's  Ergograph,  found  2:30  p.  m.  to  be  the  best 
period,  the  evening  to  be  superior  to  the  morning  and  to  the 
midnight  periods,  which  were  about  equal. 

Harley16  gives  the  following  as  the  results  of  a  six-day 
Ergographic  test: 

Hour  9     10    ii    12     i      2     3      4     5      6     7     8 

K-M  6.2  6.4  8.7  7.0  9.5  8.2  9.9  7.8  8.9  8.7  7.2  8.8 

This  shows  a  steady  rise  till  u  a.  m.,  a  slight  fall  at  noon,  a 
rise  at  I  p.  m.,  another  slight  drop  at  2  p.  m.  with  a  crest 
at  3  p.  m.  This  is  followed  by  an  irregular  decline  through 
the  rest  of  the  test  period. 

Krsepelin20  found  a  rather  unusual  variation  consisting  of 
a  gradually  increasing  efficiency  during  the  three  or  four 
hours  after  each  meal.  He  explains  this  decrease  of  muscular 


DIURNAL    VARIATIONS  49 

ability  as  the  result  of  the  increased  demands  on  the  blood 
supply  during  the  process  of  digestion.  At  least  one  German 
investigator,  Rcemer,  has  reported  similar  variations. 

Christopher6,  in  a  series  of  90  second  Ergographic  tests, 
on  1127  Chicago  school  children  at  each  hour  of  the  day,  to- 
gether with  more  extended  tests  with  four  boys  and  four 
girls,  finds  a  maximum  at  9  a.  m.,  a  slight  decrease  till  1 1 130 
a.  m.,  where  there  is  a  heavy  loss,  and  this  is  followed  by  a 
renewal  of  energy  at  I  p.  m.,  increasing  to  the  highest  point 
at  2:30  p.  m.,  whence  it  descends  till  4  p.  m.  His  results 
show  ( i )  that  there  is  a  much  greater  drop  in  efficiency  dur- 
ing the  morning  period  than  in  the  afternoon,  and  that  (2) 
strength  is  not  so  great  in  the  afternoon  as  in  the  morning. 
but  it  is  better  sustained. 

2.     DAILY  VARIATIONS  IN  VOLUNTARY  MUSCLE  CONTRAC- 
TIONS.    (STOREY)37 

(1)  Method.  During    the   year    1899,    Storey,    then    at 
Stanford  University,  tested  a  number  of  individuals  at  irre- 
gular intervals,  as  to  the  daily  variations  in  the  power  of 
voluntary  muscular  contraction.    In  the  first  tests,  Lombard's 
modifications  of  Mosso's  Ergograph  was  used.     Later  he 
used  the  Upham  Dynamometer. 

(2)  Results.     He  found  a  rise  in  power  each  morning 
till  10  or  ii  a.  m.,  a  fall  till  i  p.  m.,  a  rise  till  4  p.  m.,  and  a 
fall  till  6  p.  m.    The  morning  maximum  comes  near  1 1  a.m. 
and  the  afternoon  maximum  comes  near  4  p.  m. 

(3)  Conclusions.     The  following  is  a  summary  of  his 
more  important  conclusions : 

i — Mental  or  muscular  work  producing  partial  fatigue, 
i.  e.,  not  exhaustion,  reduces  the  power  of  voluntary 
muscular  contraction. 

2 — Sleep  and  food  restore  ability  to  work. 

3 — The  power  of  'voluntary  muscular  contraction  is 
directly  influenced  by  bodily  health. 


5O  PERIODIC   VARIATIONS    IN    EFFICIENCY 

4 — Exercise  has  an  immediate  and  stimulating  effect  on 

the  power  of  muscular  contraction. 
5 — Ordinary  variations  in  temperature  have  no  percep- 
tible effect. 

(4)  Criticism.  This  was  a  pioneer  in  the  field,  and  like 
all  pioneer  investigations,  the  method  and  procedure  are, 
perhaps,  not  so  carefully  controlled  as  they  might  be.  Many 
details  are  lacking  in  the  report,  and  the  details  are  poorly 
presented.  As  a  pioneer  work,  his  investigations  are  worthy 
of  mention. 
3.  THE  DIURNAL  COURSE  OF  EFFICIENCY.  (  MARSH  )30 

(1)  Description.     In  1906,  Marsh  began  a  series  of  ex- 
periments at  Columbia  University  dealing   with  the  daily 
variations  in  mental,  physical,  and  psycho-physical  efficiency. 
His  work  attempted  to  find  out  whether  there  are  normally 
recurring  variations  in  ability    during    the    day.     Several 
groups  of  subjects  were  investigated  for  one  or  two  days, 
and  a  few  subjects  for  several  days,  among  them  seven  grad- 
uate students,  sixteen  female  undergradute  students,  twen- 
ty-two factory  operatives  and  himself.    In  these  tests  he  not 
only  tried  to  find  out  what  was  shown  in  the  laboratory  by 
students,  but  also  just  what  people  accomplish  under  or- 
dinary conditions  of  life.     As  a  rule,  the  tests  were  given 
four  times  daily,  before  breakfast,  lunch,  dinner,  and  bed- 
time. 

(2)  Results.    The  results  from  his  different  tests  will  be 
presented  separately  according  to  the  kind  of  test  used. 

(a)  Speed  and  Accuracy  of  Movement.     In  this  test, 
which  consisted  of  striking  squares  with  a  pencil  point, 
an  inverse  ratio  of  speed  and  accuracy  is  shown,  the 
most  accurate  tests  being  from  9  to  n  a.  m.,  while  the 
best  speed  was  from  12  m.  to  2  p.  m. 

(b)  Accuracy.     In  this  test,  which  consisted  of  snap- 
ping a  wooden  disc  at  an  opening  60  cm.  distant,  the 


DiURNAt  VARIATIONS  gt 

most  accurate  results  were  made  from  12  m.  to  2  p.  m., 
and  the  least  accurate  were  made  from  4  to  6  p.  m. 

(c)  Speed.    In  this  test  for  writing  several  words,  the 
results  show  the  best  speed  from  12  m.  to  2  p.  m.,  and 
the  poorest  from  4  to  6  p.  m. 

(d)  Tapping.    These  tests  show  a  maximum  rate  from 
9  to  10  p.  m.,  with  the  greatest  accuracy  about  the  mid- 
dle of  the  day. 

(e)     Dynamometric  Grip  Tests.     These  were  taken  by 
Marsh  for  30  days  with  great  regularity  of  external 
"and  subjective  conditions,  using  the  Collins  Dynamo- 
meter.   The  average  of  grips  taken  with  the  right  hand 
*     -is  shown  in  the  table. 

7:008:30  10       11:30    1:30  3          4:30    6       7:30    9       10:30  11-12 
60.6    63    64.3     66.2     65.5     66.2     66.7     69      65.4     66        62.8    60.7 

The  results  show  a  rise  to  1 1  .'30  a.  m.,  a  slight  drop 
at  1 130  p.  m.,  a  second  rise  with  a  crest  at  6  p.  m.,  fol- 
lowed by  a  decrease  to  1 1  p.  m. 

(  f )  Work  in  Factories.  In  these  tests,  women  factory 
operatives  show,  a  low  morning  power  which  increases 
till  ii  a.  m.,  falls  slightly  till  I  p.  m.,  increases  to  a 
maximum  between  3  and  5  :3O  p.  m.,  and  falls  till  bed- 
time. 

(g)  Discrimination.  In  the  tests  for  discrimination, 
the  best  ability  was  found  at  noon,  and  the  poorest  at  the 
extreme  periods.  The  shortest  time  was  from  12  m  to 
2  p.  m.,  while  the  poorest  was  from  9  to  n  p.  m. 
(h)  Mental  Tests.  Mental  tests  were  made  in  associa- 
tion, memory,  and  addition,  all  of  which  showed  that 
from  12  m.  to  2  p.  m.  was  the  most  favorable,  and  9  to 
1 1  p.  m.,  the  least  favorable. 

(3)  Conclusions.  For  physical  abilities  including  work 
in  factories,  there  seems  to  be  a  gradual  increase  from  the 
early  morning  hours  in  tests  till  6  p.  m.,  and  in  work  till 


$2  PERIODIC  VARIATIONS   IN    EFFICIENCY 

about  3  to  5  p.  m.,  followed  by  a  decrease  in  both  cases  to 
ii  p.  m. 

For  mental  abilities,  the  tests  show  a  midday  maximum  of 
accuracy.  The  morning  is  favored  though  but  slightly.  In 
the  strictly  mental  but  more  complex  activities  there  is  a 
similar  inclination  to  the  morning  period  both  in  rate  and 
accuracy. 

(4)  Criticism,  In  this  work,  the  author  employed  a 
great  variety  of  means  in  testing  mental  and  physical  effi- 
ciency. While  the  physical  tests  are  quite  well  worked  out,' 
the  data  are  rather  weak  on  the  mental  side.  The  chief  criti- 
cism is  that  the  author  drew  his  conclusions  from  too  small 
an  amount  of  data.  His  work  should  have  been  more  ex- 
tended, and  more  daily  records  should  have  been  made  each 
day  to  give  his  conclusions  the  degree  of  validity  assumed. 
However,  the  author  used  the  methods  which  were  consid- 
ered best  at  the  time,  in  making  his  tests,  and  there  has  been 
but  little  improvement  in  the  methods  since  his  work,  so  that 
it  still  remains  the  standard  work  on  the  diurnal  course  of 
mental  and  physical  efficiency. 

4.     DIURNAL  VARIATIONS  AND  EXERCISE  EFFECTS.   (LEH- 
MAN  AND   PEDERSEN)25 

(1)  Diurnal  Variations.    Lehman  made  tests  to  discover 
diurnal  variations  during  a  period  of  four  days,  and  his  re- 
sults are  shown  in  the  following  table: 

9  A.  M.  (after  breakfast)  32.5  Kilos 

i  P.  M.  (before  a  2-hour  walk)  31.8 

3  P.  M.  (after  a  2-hour  walk)  35.3 

ii  P.  M.  (before  retiring)  30.9 

(2)  Exercise.     Pedersen  made  a  similar  series  of  tests. 
taking  a  walk  of  from  2  to  4  hours  duration  at  different 
times  of  day  with  the  following  results : 


DIURNAL    VARIATIONS  53 

On  level  ground  On  rising  ground 
Record  made  before  walk       37.2  Kilos  36.8  Kilos 

Half  way  37.8      " 

Top  of  rising  ground  37.9 

Record  made  on  return          38.0  38.4 

The  first  of  these  shows  the  influence  of  the  time  of  day, 
while  both  show  the  beneficial  effects  of  the  two  hours'  walk. 
They  also  show  that  only  those  tests  taken  in  the  morning 
before  work  are  rigidly  comparable,  as  the  kind  of  work  done 
during  the  day  has  its  effects  on  the  results.  The  greater 
increase  in  muscle  strength  on  the  high  ground,  shows  the 
beneficial  effects  of  lowering  the  atmospheric  pressure. 

5.     DIURNAL    VARIATIONS    IN    MUSCULAR    ENERGY. 

(KUHNES)21 

(1)  Description.     Kuhnes,  whose  work  I  have  already 
reported  under  "Seasonal  Periodicity,"  made  a  thorough  in- 
vestigation   of    diurnal    periodicity    as    shown    in    muscle 
strength.    Each  day,  for  505  consecutive  days,  he  took  three 
tests  with  each  hand  in  three  different  positions,  alternately 
with  the  right  and  left  hand,  seven  times  daily,  making  in  all 
twenty-one  tests  with  each  hand  each  day.     The  tests  were 
very  carefully  controlled,  and  in  order  to  eliminate  the  ef- 
fects of  holding  the  dynamometer  in  different  positions,  the 
three  positions  were  always  the  same  and  taken  in  the  same 
order,  viz. — (i)   each  hand  hanging  down,   (2)   each  hand 
held  vertically,  and  (3)  each  hand  held  horizontally. 

(2)  Results.     The  results  cover  about  26,500  measure- 
ments, and  the  averages  are  somewhat  as  follows :  At  7  a.  m. 
comes  a  relatively  low  measurement  followed  by  a  rapid  rise 
at  9  a.  m.,  a  slight  drop  at  12  m.,  a  small  rise  at  2  p.  m., 
which  is  the  best  time  of  all,  a  small  drop  at  6  p.  m.,  a  slight 
rise  at  8  p.  m.  and  a  decided  drop  at  1 1  p.  m.    The  average 
results  for  each  hour  during  the  whole  period  is  shown  in 
the  accompanying  table. 


54  PERIODIC   VARIATIONS    IN    EFFICIENCY 

7  a.m.  9  a.m.  12  m.     2  p.m.   6  p.m.  8  p.m.  11  p.m. 

Average  43-5  46.5  46.5  46.8  46.5  46.7  45-3 

Maximum  49  50.6  52.0  50.8  50.8  51.1  50.6 

Minimum  38.5  39  36  41. 5  4O.8  43.0  40.6 
Diff.  of  Max. 

and   Minimum  10.5  n.6  14  9.3  10  8.1  10 

Median  43.6  46.8  46.7  47.1  46.9  47-3  45-9 

Mean    Variant.  1.5  1.7  1.8  1.7          1.7  1.8          1.8 

(3)  Conclusions.    There  is  a  distinct  diurnal  course  of 
efficiency  which  starts  low,  rises  till  12  m.,  drops  slightly, 
but  rises  again  showing  its  crest  at  2  p.  m.     In  the  after- 
noon there  is  a  drop  at  6  p.  m.,  a  small  rise  at  8  p.  m.,  fol- 
lowed by  a  rapid  decrease  till  n  p.  m.    The  average  curve 
here  described  is  also  the  curve  of  68  per  cent,  of  the  505 
days. 

From  the  valuable  introspections  which  he  kept  each  day, 
he  concludes  that  physical  fatigue  or  physical  inactivity  cause 
a  marked  decrease  in  physical  strength,  while  mental  fatigue 
has  an  influence  that  differs  from  that  shown  by  physical 
fatigue. 

(4)  Criticism.     This   work  has   been   criticised  before, 
but  I  will  add  here  that  it  is  the  most  complete  record  of  diur- 
nal efficiency  covering  a  long  period  of  time,  which  has  ever 
been  made.    All  the  data  are  given  in  complete  form,  and  a 
most  careful  search  fails  to  show  any  errors  in  the  method, 
or  in  the  interpretation  of  the  results. 

6.  VARIATIONS  IN  EFFICIENCY  DURING  THE  DAY.  ( GATES)  ll 
(i)  Method.  During  the  year  1913-4,  while  a  student  at 
the  University  of  California,  Gates  attempted  to  discover 
diurnal  rhythms  of  efficiency  by  a  variety  of  mental  and 
physical  tests.  The  subjects  were  pupils  of  the  fifth  and 
sixth  grades  in  the  public  schools.  During  the  five  days  of 
the  tests,  each  class  was  divided  into  five  groups  of  about 
eight  pupils  each.  Each  group  was  tested  separately  at 
9  a.  m.,  10  a.  m.,  n  a.  m.,  I  p.  m.  and  2  p.  m.  On  each  suc- 
ceeding test  day,  each  group  except  that  tested  last  was 
tested  one  hour  later  than  before,  while  the  one  previously 


DIURNAL,    VARIATIONS  55 

tested  last,  was  tested  first.  In  this  way  each  group  was 
tested  at  a  different  hour  each  test  day,  and  once  at  each  of 
the  hours  mentioned  above. 

(2)  Results.  The  table  here  given  show  the  combined 
record  for  all  six  classes  in  per  cent.,  the  first  record  being 
used  as  a  base. 

Hours  9-10  lo-n  11-12          1-2  2-3 

Addition  tests  100  102.4  104.2  102.3  103 

Multiplication  tests  100  101.9  105.1  100.9  103 

Auditory  Memory  100  105.9  106.7  994  102.4 

Visual   Memory  100  103.2  109.2  99.06  103.4 

Recognition  tests  100  104.7  105.9  100  103.7 

Maze  Test — speed  100  100.34  100.93  108.9  112.2 

Maze  Test  accuracy  100  102.9  104.2  98.2         96 

Completion  tests  100  105  109.7  106.2  108.8 

Cancellation  tests  100  101.8  104.4  194-9  IO5-5 

Summarizing  the  results  we  find  that  in  the  addition, 
multiplication,  memory,  recognition,  and  completion  tests 
there  is  a  more  or  less  steady  rise  in  efficiency  from  9  a.  m. 
to  noon,  followed,  by  a  decrease  of  differing  but  always 
noticeable  extent  at  I  p.  m.  and  a  subsequent  rise  during  the 
last  hour. 

In  the  speed  and  accuracy  tests,  and  in  the  cancellation 
test,  there  is  a  steady  rise  through  the  day  with  a  maximum 
at  the  end.  Speed  is  greater,  but  accuracy  less  in  the  after- 
noon, therefore  it  would  seem  that  speed  is  attained  at  the 
expense  of  accuracy. 

All  of  the  functions  tested  show  improvement  due  to  prac- 
tice effects,  varying  from  7  to  33.3  per  cent.  There  are  no 
sex  differences,  or  effects  of  fatigue,  temperature  changes, 
humidity,  or  weather  in  general  shown  in  this  study.  The 
author  finds  high  correlations  only  in  the  two  arithmetical 
and  in  the  two  memory  tests,  while  in  the  others,  the  cor- 
relations except  in  related  functions  do  not  amount  to 
much,  and  that  in  such  dissimilar  tests  the  correlation  re- 
sults are  largely  a  matter  of  accidents. 


56  PERIODIC    VARIATIONS    IN 

He  concludes  that  the  strictly  mental  activities  are  more 
affected  by  fatigue  than  are  the  motor  activities  or  those 
which  involve  muscle  strength,  the  first  showing  a  maximum 
in  the  late  afternoon  while  motor  functions  show  a  contin- 
uous increase  throughout  the  whole  school  day. 

(3)  Criticism.  The  account  of  this  investigation  is  well 
written  and  the  author  shows  a  broad  and  comprehensive 
knowledge  of  the  work  of  other  investigators  in  similar  and 
related  fields.  In  the  tests  used,  in  nearly  every  case  the 
time  given  was  far  too  short  for  all  the  children  to  perform 
the  tasks  demanded,  so  that  after  the  children  found  out 
they  could  not  do  all  of  any  test  within  the  time  limit,  haste 
was  probably  a  prolific  source  of  error.  It  seems  also  that 
while  the  tests  covered  a  great  variety  of  functions,  they 
were  too  few  in  number  to  warrant  any  universal  conclu- 
sions, and  it  is  to  be  regretted  that  preliminary  and  verifying 
tests  were  not  made.  However  the  author  recognizes  the 
limitations  of  his  results,  and  does  not  draw  any  fanciful  con- 
clusions which  are  unjustified  by  the  results.  The  range  of 
the  tests  and  the  care  with  which  they  were  given,  gives 
much  validity  to  the  results,  which  agree  closely  with  those  of 
other  American  investigators  in  this  field.  It  is  easily  the 
best  of  its  kind,  and  it  must  be  taken  into  account  by  all 
future  investigators  of  diurnal  variations  in  mental  abilities. 
7.  DIURNAL  VARIATIONS  IN  MEMORY  AND  ASSOCIATION. 

(GATES)12 

(i)  Method.  Gates  supplemented  his  first  investigation 
by  a  series  of  memory  and  association  tests  made  on  groups 
of  from  six  to  fourteen  college  students,  numbering  165  in 
all.  The  tests  were  made  at  each  hour  of  the  day  from  8 
a.  m.  to  5  p.  m.,  excepting  only  the  noon  hour.  Before  taking 
the  tests  each  student  was  asked  to  state,  among  other 
things,  the  time  of  day  when  he  felt  he  could  do  his  most 
and  best  work.  Tests  were  given  in  auditory  memory, 


DIURNAt   VARIATIONS  $7 

visual  memory,  substitution,  recognition,  and  logical  mem- 
ory (Healy  Test). 

(2)  Results.    The  average  results  in  per  cent  for  each  of 
the  various  tests  is  here  given. 

Hour                   89         10       ii  12  3  4  5 

Auditory  memory  100    97-5    98.8  103.3  974    94-5  98.2    95.5  93.8 

Visual  memory  100    99.3  101.5  101.5  98.0  100.1  101.7  102  100 

Substitution  100  102.7  195.2  104.3  96.0  102.6  101.5  101.2  94.3 

Recognition  TOO  115.7  122.2  115.7  Joo-5  in  120      120  116.5 

Logical    memory  100  109     107.7  103  95.5    99.3  101.4  102.2  91.3 

Avg.  of  all  tests  100  104.3  106.6  105.6  98.7  100.6  105.1  104.2  100.4 

The  results  from  all  these  tests  show  a  great  similarity. 
Beginning  at  8  a.  m.,  all  the  curves  rise  till  10  and  some  till 
ii  a.  m.  The  I  p.  m.  figure  is  quite  low  in  all  tests  and  al- 
ways lower  than  the  late  afternoon. 

(3)  Conclusions.    In  the  subject's  own  estimates  of  their 
best  hour,  many  choose  too  early  an  hour,  few  choose  10 
a.  m.  or  n  a.  m.,  and  practically  none  choose  the  late  after- 
noon hours.     From  this  Gates   draws  the   conclusion  that 
one's  subjective  feelings  with  regard  to  the  time  of  greatest 
efficiency,  are  not  reliable.    The  hours  of  greatest  efficiency 
are  those  at  which  fatigue  (it  would  seem),  should  be  very 
great.    A  man  should,  therefore,  by  practice  in  the  voluntary 
disregard  of  the  mere  feelings  of  fatigue  learn  the  limits  of 
his  ability  and  thus  attain  greater  efficiency. 

(4)  Criticism.    In  this  series  of  tests  the  author  used  sev- 
eral well  known  methods  for  testing  efficiency  in  the  field  of 
immediate  memory  and  association.     The  investigation   is 
valuable  chiefly  from  the  fact  that  such  a  large  group  (165 
college  students)  were  given  such  a  variety  of  tests  for  pur- 
poses of  comparison.    It  is  to  be  regretted,  however,  that  the 
experiments  lasted  only  three  days,  and  that  on  the  days 
mentioned,  the  subjects  spent  the  time  in  continuously  taking 
tests.     The  questionnaire  submitted  to  each  student  before 
taking  the  tests,  brought  out  some  very  interesting  facts,  and 


58  PERIODIC  VARIATIONS   IN    EFFICIENCY 

shows  one's  own  opinion  of  his  best  working  hoiirs  is  hot 
reliable. 

8.     SUMMARY  OF  PROBLEMS  AND  RESULTS  IN  DIURNAL 
PERIODICITY. 

The  diurnal  course  of  efficiency  seems  to  be  pretty  well 
established  both  for  mental  and  physical  abilities.  In  both 
cases,  all  previous  investigators  have  found  both  a  morning 
and  an  afternoon  crest.  The  records  for  variations  in  phy- 
-DBJ  in  jjaoM  puB  s9i;iApDB  jojoui  Suipnpui  'SDuqiqc  JEDIS 
tories,  show  a  continuous  increase  in  the  morning  till  about 
ii  a.  m.,  a  slight  drop  from  12  m.  to  I  p.  m.,  with  a  further 
rise  to  a  maximum  sometime  between  3  and  6  p.  m.  The 
results  for  mental  work  show  a  more  or  less  steady  rise  till 
ii  a.  m.,  a  slight  drop  around  noon  with  a  new  high  level 
around  2  p.  m.,  then  a  gradual  decrease  till  the  close  of  the 
day.  Kuhnes  found  that  in  many  cases  physical  strength 
grows  continuously  till  about  8  p.  m.,  after  which  it  declines. 
This  fact  was  also  noted  in  some  factory  workers  by  Marsh. 

In  Speed  and  Accuracy  Tests,  accuracy  is  better  in  the 
morning  and  speed  greater  in  the  afternoon,  a  result  which 
seems  to  show  that  speed  is  often  gained  at  the  expense  of 
accuracy. 

Kuhnes  found  in  a  test  covering  505  consecutive  days  that 
the  average  daily  curve  in  dynamometric  tests  is  also  the 
curve  for  68  per  cent,  of  the  days.  This  would  seem  to  indi- 
cate the  great  importance  of  diurnal  variations  in  any  study 
of  seasonal  periodicity. 

9.    DIURNAL  PERIODICITY  IN  MY  ORIGINAL  EXPERIMENTAL 
INVESTIGATION. 

In  my  own  investigation,  through  October,  November  and 
December,  the  B.  division  was  tested  at  various  hours  from 
9  a.  m.  to  3  p.  m.  After  January  the  tests  were  always  given 
between  2  p.  m.  and  3  p.  m.  The  following  table  shows  the 
distribution  of  variations  I  Kg.  from  the  weekly  average  in 
grip  strength. 


DIURNAt   VARIATIONS  59 

Hour  of  the  Day           9  to  10  10  to  n  n  to  12  1  to  2  2  to  3 
Per  cent,  of  tests  given 

at  each  hour  20  8  8            24  40 
Per  cent  of  test  varying* 

I  Kg.  from  the  average  12  12  12            30  30 

i  Kg.  above  the  average  5  10  15            35  35 

i  Kg.  below  the  average  30  20  10            20  20 

Rank  54312 

These  data  seem  to  show  a  diurnal  course  of  efficiency 
which  rises  continuously  from  9  a.  m.  to  3  p.  m.  for  muscle 
energy.  The  exceptionally  low  records  made  at  10  to  n 
a.  m.  and  at  I  to  2  p.  m.  were  made  during  the  first  week. 
There  was  no  test  made  at  9  a.  m.  until  Monday  of  the  third 
week,  so  we  find  these  low  records  at  the  other  hours.  In 
spite  of  this  fact,  however,  the  average  of  the  9  a.  m.  records 
is  the  lowest  of  all  the  hours  shown  as  can  be  seen  in  the 
following  table : 

RIGHT  HAND  LEFT  HAND 

Hour  9-10  10-11  u-12     1-2  2-3  Hour  9-10  10-11   11-12    1-2  2-3 

Avg.    47.7    48.8    48.9    49-3  Si-*  Avg.     44.5    44.7    45       46  46.3 

High    50.1     54.3    54.4    55.3  57.1  High    46.6    49.9    50.4    5*  53-6 

Low     43.7    43.3    46.1     42.6  43.0  Low     42.3    39.5    41       42.4  40 

These  results  agree  with  those  of  other  investigators  in 
showing  muscle  energy  increases  almost  continuously  from 
9  a.  m.  to  at  least  3  p.  m. 

The  results  for  memory  show  a  similar  tendency  except 
for  a  greater  depression  from  1 1  a.  m.  to  i  p.  m.,  as  can  be 
seen  from  the  following  table : 

MEMORY  FOR  15  NUMBERS 

Hour                          9-10           10-11         11-12  i-e  2-3 

Average                             10.1             10.7            10  10.1  10.5 

High                                   10.9            11.7            11.2  11.9  n.6 

Low                                    9.5             8.3             8.2  8.8  8.8 

MEMORY  FOR  4  NUMBERS 

Hour  9-10  lo-u         11-12  I-Q  2-3 

Average  3-56  3.65  345  3.64  3-68 

4  3-9  3-8  4  4 

2.5  3.3  2.8  3.2  3.3 


60  PERIODIC    VARIATIONS    IX    EFFICIENCY 

MEMORY   FOR   5    NUMBERS 

Hour  9-10  10-11          11-12  1-2  2-3 

Average  3-32  3.65  3.03  347  3-34 

High  3-7  4-3  3-3  4-6  3-9 

Low  2.9  2.5  t          2.8  2.6  2.8 

MEMORY  FOR  6   NUMBERS 

Hour                           9-10           lo-u          11-12  i-<2  2-3 

Average                               3-2              3-4              2.9  3.1  3.5 

High                                     4.1              4                 3.8  3.9  4-3 

Low                                      2.9              2.5              2.3  2.5  3.4 

In  all  probability  the  results  for  the  series  of  five  numbers 
aie  the  most  reliable.  The  series  of  four  numbers  served 
as  a  sort  of  preliminary  test  to  fix  the  attention  on  the  task, 
and  to  warm  subjects  up  to  the  work.  The  series  of  six 
numbers  was  perhaps  too  long,  a  perfect  score  being  very 
rarely  made.  These  results  for  primary  memory  all  show  a 
rise  from  9  to  n  a.  m.,  a  drop  from  n  a.  m.  to  I  p.  m.,  a 
rise  from  I  p.  m.  to  2  p.  m.  and  a  slight  drop  from  2  to  3 
p.  m.  in  some  cases,  while  in  other  the  records  from  2  to  3 
p.  m.  remain  almost  stationary.  The  results  from  the  A. 
division  were  almost  all  made  between  2  and  3  p.  m.,  so  that 
they  add  nothing  to  the  results  on  diurnal  periodicity. 


CHAPTER   V. 

OTHER  PERIODIC  VARIATIONS  IN  MENTAL  AND 
PHYSICAL  ABILITIES 

1 I )  Introduction.    Besides  the  diurnal  and  seasonal  vari- 
ations, there  have  been  many  other  suggestions  as  to  periodic 
variations  in  mental  and  physical  abilities.    Among  those  we 
find  the  so-called  Twenty-eight  Day  period,  the  Twenty-three 
Day  period,  and  the  Seven  Day  or  weekly  period. 

(2)  Twenty-eight     Day     Periodicity.     Malling-Hansen 
first  suggested  that  vital  force  was  subject  to  periodic  varia- 
tions every  twenty-eight  days.    Of  course  there  is  no  doubt 
about  the  twenty-eight  day  periods  in  females,  but  the  exist- 
ence of  twenty-eight  day  periods   in  mental  and  physical 
abilities  has  never  been  firmly  proven  or  disproven  as  yet. 
This  is  due  to  the  fact  that  such  periods  would  vary  with 
the  individuals  and  investigators  have  been  much  more  in- 
terested in  results  from  large  numbers  than  from  individuals. 

Dr.  Kuhnes  has  given  this  problem  more  attention  than 
any  other  investigator.  In  this  investigation  in  variations  in 
physical  ability,  he  arranged  the  data  in  a  series  of.  thirteen 
twenty-eight  day  periods,  counting  twenty-eight  day  periods 
from  the  day  of  his  birth.  His  results  when  so  arranged, 
show  a  marked  variation  through  the  first  three  days,  an 
almost  constant  value  from  the  fourth  to  the  twentieth,  and 
more  or  less  irregularity  from  the  twenty-first  to  the  twenty- 
eighth  day.  The  highest  points  are  found  on  the  twenty- 
second,  twenty-third,  and  twenty-fourth  days,  while  the  low- 
est point  is  found  on  the  third  day.  Dr.  Kuhnes  comes  to 
the  conclusion  from  his  remarks  that  they  gave  little  warrant 
for  assuming  the  existence  of  a  twenty-eigfit  day  period  in 
muscle  strength, 

61 


62  PERIODIC   VARIATIONS    IN    EFFICIENCY 

My  own  data  are  not  arranged  in  a  suitable  form  for  a 
comparison  with  the  results  of  others  as  to  the  existence  of  a 
twenty-eight  day  rhythm. 

(3)  Twenty-three    Day    Periodicity.      Stohr    describes 
briefly  a  Twenty-three  Day  rhythm  found  independently  by 
two  Germans,  Fleiss  and  Svoboda.    Each  of  these  men  claim 
to  have  found  a  twenty-three  day  period  in  mental  and  phy- 
sical abilities  on  the  basis  of  personal  observation,  Svoboda 
claiming   that   ideas    automatically    and    spontaneously    re- 
appear in  the  mind  every  twenty-third  day. 

So  far  as  I  know,  no  American  investigator  has  found 
similar  results.  Dr.  Kuhnes  arranged  his  data  in  twenty- 
three  day  periods  counting  from  birth.  His  curve  for  aver- 
ages shows  a  nearly  straight  trend  for  17  days,  then  rises 
slightly  till  the  end  of  the  22  day,  and  shows  a  rise  of  seven 
kilos  on  the  twenty-third  day.  This  variation  is  nearly 
double  the  rise  and  fall  on  any  other  day.  The  median  curve 
shows  a  gradual  decline  until  the  tenth  day,  a  sudden  drop 
on  the  eleventh  day,  with  a  gradual  rise  to  the  end  of  the 
period.  The  9  a.  m.  records  show  a  distinct  rise  on  the 
twenty-third  day,  but  the  point  reached  is  not  higher  than 
that  on  the  fourteenth  day.  He  concludes  that  while  there 
are  some  unexpected  peculiarities  in  his  results  for  the 
twenty-third  day,  his  data  do  not  warrant  a  general  ac- 
ceptance of  the  twenty-three  day  period, 

In  this  field,  as  in  the  twenty-eighth  day  period,  my  own 
data  cannot  be  arranged  in  a  way  that  would  be  comparable 
with  the  results  of  others,  or  to  show  any  twenty-three  4ay 
periods. 

(4)  Weekly  Periodicity. 

(i)  Introduction.  Weekly  periodicity  has  not  been  in- 
vestigated to  any  considerable  extent.  The  fact  that  for 
many  generations  people  in  many  lands  have  ordered  their 
lives  by  seven  day  periods  would  suggest  the  possibility  of  a 
seven  day  period  in  mental  and  physical  abilities. 


OTHER  PERIODIC  VARIATIONS  63 

(2)  Huntington19.    Huntington  found  that  on  the  whole, 
the  curves  of  work  done  by  pieceworkers  are  higher  at  the 
end  of  the  week  than  at  the  beginning,  Monday  being  low, 
and  Thursday  and  Friday  the  highest,  with  a  falling  off  on 
Saturday.     He  gives  the  following  table  for  piece-workers 
in  a  Cuban  factory. 

Mon.       Tues.       Wed.      Thur.      Fri.        Sat. 
81.9        98.7        99.8          loo        98.         97.9 

(3)  Kuhnes.21    Kuhnes  studied  the  averages  of  42  daily 
tests  for  fifty-three  weeks  with  the  following  results : 


Days 

Sun. 

Mon. 

Tue. 

Wed. 

Thu. 

Fri. 

Sat. 

Average 

46  Kg. 

45-9 

46.3 

46.1 

45-9 

46 

46.3 

Maximum 

49-1 

49-3 

49-5 

48.9 

48.7 

49 

48.9 

Minimum 

42.9 

42.0 

43-2 

43-1 

4L5 

42.8 

43-2 

Diff.  of  M-M 

6.2 

7-3 

6-3 

5.8 

7.2 

6.2 

5-7 

Mean  Var. 

1.53 

1.66 

1.43 

1-34 

1.31 

1.53 

1-33 

Median 

45-5 

46.1 

46.6 

46.3 

46.1 

45-8 

46.3 

In  this  table,  Mondays  and  Thursday  show  the  lowest 
averages  being  4  kg.  below  the  maximum  reached  on  Tues- 
days and  Saturdays.  Kuhnes  found  that  the  weekly  curve 
followed  very  closely  that  of  the  days  of  the  most  and  least 
study,  and  that  hard  study  with  a  lack  of  exercise  caused 
low  records. 

5.    WEEKLY  PERIODICITY  IN  MY  ORIGINAL  EXPERIMENTAL 
INVESTIGATION. 

In  an  endeavor  to  discover  any  traces  of  a  weekly  period 
in  my  own  results,  I  first  tabulated  the  daily  distribution  of 
the  averages  I  Kg.  from  the  averages  for  the  week,  and 
give  them  in  the  following  table  in  per  cent. 

Right   Hand  Left  Hand 

Day  Above        Below  Above  Below  Rank 

Monday  9  18  6  25  5 

Tuesday  12  12  o  16  4 

Wednesday  9  o  II  32 

'Thursday  9  o  9  3  I 

Friday  19  12  16  n  3 


64  PERIODIC    VARIATIONS    IN    EFFICIENCY 

These  results  show  that  Monday  is  the  poorest  day  while 
Thursday  is  the  best.  Monday  and  Friday  are  more  variable, 
but  on  Monday  the  variations  tend  to  fall  below  the  line  of 
weekly  averages,  while  on  Friday  they  tend  to  rise  above  it. 
The  number  of  such  variations  on  Wednesday  and  Thursday 
is  small,  and  almost  all  of  them  are  above  the  average  for 
the  week. 

According  to  these  data,  Monday  is  low,  and  is  followed  by 
an  irregular  rise  through  the  week  to  a  crest  on  Thursday. 
This  is  followed  by  a  slight  drop  on  Friday.  The  following 
tables  show  the  results  for  the  Memory  and  Grip  Tests  by 
days  for  each  month. 


Day  Mon.  Tue.  Wed.  Thu.  Fri. 

Oct.  R.  45.2  46.6  46.4  45.8  45.6 

42.6 
Nov.  •  R.  50.8  49.6  50.4  49.3  48.9 

46.5 
Dec.  R.  53.5  534  5i-6  52.3  52-7 

49-7 
Jan.  R.  53-4  54-2  54-7  54-5  54-6 

51-3 
Feb.  R.  54  54  54.4  54.2  54.2 

51-9 
Mch.  R.  54.7  54.6  56.5  56.2  57-3 

52-5 
Apr.  R.  55.2  56.4  56.5  56.2  57-3 

54-3 
May  R.  58.3  59.  i  59- 1  5&9  56.3 

54-9 


Oct.  10.2  8.8  9  9-7  9-6 

Nov.  10  ii. i  10.4  19.1  10.1 

Dec.  1 1. 1  ii  10.8  10  ii 

Jan.  10.3  10.3  10.4  10.3  ii 

Feb.  9-8  9-9  10.3  10.5  10 

Mch.  10.9  10.9  10  10.3  19-3 

Apr.  1 1. 6  1 1. 6  10.7  11.4  10.6 

May  11.4  ii. i  ii  11.5  H-6 


GRIP   TABLE 

Mon. 

Tue. 

Wed. 

Thu. 

R. 

45-2 

46.6 

46.4 

45-8 

L. 

42.1 

41.7 

43-2 

43 

R. 

50.8 

49-6 

50.4 

49-3 

L. 

47.2 

46.7 

47.2 

454 

R. 

53-5 

534 

51-6 

52.3 

L. 

50.6 

48.6 

49.2 

49-7 

R. 

53-4 

54-2 

54-7 

54-5 

L. 

50-8 

5i.i 

51-7 

50.8 

R. 

54 

54 

54-4 

54-2 

L. 

5i 

50-7 

50-7 

51-4 

R. 

54-7 

54-6 

56.5 

56.2 

L. 

52-4 

53 

52.8 

52.9 

R. 

55-2 

56.4 

56-5 

56.2 

L. 

53-6 

54-7 

52.6 

54-2 

R. 

58-3 

59.1 

59-1 

58.9 

L. 

53-6 

55-4 

55-9 

55-2 

MEMORY 

TABLE 

(15  points) 

10.2 

8.8 

9 

9-7 

10 

ii.  i 

10.4 

19.1 

II.  I 

ii 

10.8 

10 

10.3 

10.3 

10.4 

10.3 

9-8 

9-9 

10.3 

10.5 

10.9 

10.9 

10 

10.3 

11.6 

1  1.6 

10.7 

1  1-4 

11.4 

ii.  i 

ii 

"•S 

OTHER  PERIODIC  VARIATIONS  65 

The  table  for  memory  does  not  show  any  pronounced 
weekly  periodicity  for  all  the  months  of  the  year.  In  Oc- 
tober, December,  March,  and  April,  the  first  part  of  the 
week  seems  to  be  more  favorable,  but  in  January,  February, 
and  May  the  reverse  is  true.  In  November  the  middle  of 
the  week  seems  preferable. 

The  results  from  the  Dynamometric  Tests  show  a  similar 
lack  of  any  weekly  periodicity.  In  November  and  Decem- 
ber, the  early  part  of  the  week  is  preferable,  but  in  February 
and  April,  the  opposite  is  true.  Wednesday  is  very  favorable 
in  ..October,  November,  January,  and  May,  while  in  March 
there  does  not  seem  to  be  much  choice.  From  the  data  as 
presented,  therefore,  we  are  not  warranted  in  assuming  that 
ffiere  is  any  weekly  periodicity  shown  either  in  the  mental  or 
physical  tests. 


CHAPTER  VI. 

WEATHER  INFLUENCES 

(1)  Introduction.     Many  statements  have  been  made  in 
literature  about  the  effects  of  various  kinds  of  weather  on 
human  thought  and  action,  but  very  little  has  been  done  to 
test  these  opinions  in  a  scientific  way.    Of  late,  two  or  three 
investigators  have  attempted  to  discover  some  existing  rela- 
tions between  the  variations  in  the  amount  of  sunshine,  tem- 
perature, humidity,  and  air  pressure  on  the  one  hand,  and  in 
the  physical,  mental,  and  moral  life  of  the  individual  on  the 
other.     One  writer,  Huntington,  points  out  the  very  close 
relation  between  various  types  of  civilization  and  climatic 
conditions,   and   concludes   that   climatic   conditions   are  as 
important  factors  in  civilization  as  are  the  oceans,  lakes, 
rivers,  mountains,  and  natural  resources. 

While  the  author  does  not  expect  to  come  to  any  unusual 
conclusions  in  this  regard,  the  results  as  here  shown  may 
give  additional  proof  to  facts  already  well  established.  The 
first  task,  however,  will  be  to  give  a  brief  review  of  the 
work  already  done  in  this  field. 

(2)  General  Weather  Effects. 

(a)  Conduct  and  the  Weather.  (Dexter).7 
The  first  American  to  investigate  the  effects  of  the 
weather  to  any  extent,  was  Dexter,  who  tried  to  study  the 
relations  of  conduct  and  the  weather.  The  questionnaire, 
supplemented  by  various  public  and  private  records  on 
crime,  insanity,  and  school  conduct,  and  the  U.  S.  Govern- 
ment records  on  weather  conditions  were  used  as  sources  for 
the  data.  In  each  case  the  relationship  established  is  purely 
statistical,  based  on  the  probability  or  expectancy  of  occurr- 
ence, all  the  data  being  arranged  to  show  the  actual  distribu- 
tion of  the  occurrence,  as  compared  to  the  expected  distribu- 

66 


WEATHER    INFLUENCES  67 

tion  of  the  occurrence.  In  this  study  were  included  data  from 
the  records  of  attendance  and  discipline  in  the  public  schools 
of  New  York  City  and  Denver,  police  records  of  Assault 
and  Battery,  Murder,  Insanity,  Suicide,  and  Death ;  Clerical 
Errors  in  a  number  of  New  York  City  banks,  and  data 
from  laboratory  experiments  made  at  Columbia  University. 
These  are  compared  with  government  records  of  tempera- 
ture, humidity,  wind,  and  character  of  the  day. 

(1)  Results.    The  results,  with  complete  descriptions  of 
the  data,  tables,  and  graphs,  are  described  in  detail,  and  from 
them  the  following  general  conclusions  are  drawn : 

i — Males  are  more  influenced  by  weather  conditions 
than  females,  and  boys  are  more  influenced  than  girls. 

2 — Precipitation  has  little  or  no  effects  at  all. 

3 — Barometric  changes  influence  largely  through  the 
production  of  other  states  of  weather,  rather  than  directly. 

4— Medium  conditions  of  humidity  are  more  favorable 
than  extremes  in  either  direction. 

5 — Time  of  year  has  no  marked  effects  on  conduct. 

6 — Varying  weather  conditions  affect  directly  the  meta- 
bolism of  life. 

7 — Reserve  energy  is  influenced  to  a  marked  degree  by 
weather  conditions. 

8 — The  quality  of  emotional  states  is  plainly  influenced 
by  the  weather. 

9— Conduct,  death,  physical  labor,  and  intellectual  ac- 
tivities, bear  very  different  relations  to  reserve  energy. 

10 — Those  weather  conditions  which  are  productive  of 
misconduct,  in  a  broad  sense  of  the  word,  are  also  pro- 
ductive of  health  and  mental  alertness,  and 

ii — Misconduct  is  the  result  of  an  excess  of  reserve 
energy  not  directed  to  more  useful  purposes. 

(2)  Criticism.    The  aim  of  this  investigation  was  a  very 
worthy  and  necessary  one,  and  while  the  method  of  select- 
ing the  data  might  be  improved  upon,  the  author  had  a  vast 


68  PERIODIC    VARIATIONS    IN    EFFICIENCY 

amount  of  materials  at  his  disposal.  The  chief  defect  is 
that  only  statistical  use  was  made  of  the  data.  In  this  way, 
the  only  thing  that  can  be  indicated  is  the  statistical  com- 
parison between  the  expected  and  the  actual  occurrence  of 
phenomena,  all  the  discussions  and  conclusions  being  based 
on  this  artificial  relationship.  What  is  shown  is  a  probable 
relationship  based  on  a  statistical  estimate  of  the  occurrence 
of  phenomena,  rather  than  any  actual  relationship  between 
the  variations  in  the  phenomena.  In  this  way  the  actual 
effects  of  changes  in  the  temperature,  humidity,  air  pres- 
sure, as  well  as  those  of  unusual  combinations  of  atmospheric 
conditions  are  almost  entirely  unnoticed.  Then  again,  the 
data  from  the  questionnaires,  should  have  received  little 
weight  unless  the  opinions  expressed  were  supported  by  rec- 
orded observations,  as  many  instances  have  been  shown 
where  the  opinions  of  individuals  are  contrary  to  the  real 
facts.  We  should,  therefore,  exclude  that  part  of  the  re- 
sult which  is  based  on  such  data.  In  the  light  of  these  facts 
it  will  not  do  to  give  too  much  weight  to  his  results  and 
conclusions.  We  must,  however,  recognize  that  this  is  a 
pioneer  work,  and  give  it  credit  for  being  what  the  author 
claims  for  it,  "A  modest  contribution  to  the  knowledge  on 
the  subject." 

(b)  Civilization  and  Climate.  (Huntington).19 
Huntington  discusses  many  phases  of  weather  and  climate 
in  its  relation  to  civilization  and  to  the  activities  of  mankind 
in  general.  Incidentally,  the  author  collects  such  data  con- 
cerning the  influence  of  the  weather  on  the  quantity  of  work 
done  by  factory  workers  in  various  parts  of  the  United 
States  and  Cuba,  and  gives  his  results.  Among  factory 
workers  in  New  Haven,  the  lowest  point  of  efficiency  is  in  the 
last  half  of  January.  It  rises  slowly  to  June,  drops  slightly 
through  July  and  August,  rises  quickly  in  September,  and 
culminates  around  the  first  of  December, 


WEATHER    INFLUENCES  69 

He  gives  several  graphs  of  work  done  by  factory  workers 
in  various  parts  of  the  United  States,  all  of  which  are  similar. 
Further  south  the  culmination  comes  a  little  later  in  the  sea- 
son and  varies  from  sometime  in  November  in  New  Haven, 
to  the  middle  of  December  in  South  Carolina  and  Florida. 
Southern  workers  also  show  a  disposition  to  hold  the  high 
level  till  about  the  middle  of  January,  while  farther  north 
they  show  a  decrease  in  working  capacity  somewhat  earlier, 
(c)  Effects  in  Weather  on  Ability  to  Learn.  (Lehman)25 
Lehman  conducted  a  series  of  tests  to  discover  the  effects 
of  weather  on  ability  to  learn  rows  of  syllables  by  heart. 
The  subjects  were  several  university  students  and  the  tests 
lasted  from  October,  1905,  to  March  of  the  following  year. 
VA  .device  was  used  which  allowed  'but  one  syllable  to  be 
visible  at  a  time.  One  hundred  thirty  rows  of  16  syllables 
each  were  prepared.  Each  syllable  was  presented  for  .75 
seconds  and  the  full  rows  were  presented  at  intervals  of 
three  seconds.  The  subjects  were  scored  on  the  number 
of  repetitions  necessary  before  being  able  to  give  a  perfect 
reproduction  of  the  row.  The  results  appear  in  the  follow- 
ing table  : 

Sep.    Oct.    Nov.    Dec.    Jan.    Feb.    Mch.    Apr.    May    Jun. 
518     521      559     528     618     555     612     549     642      553 

This  shows  a  rise  to  a  high  level  in  January,  a  drop  for 
February,  a  quick  rise  in  March,  and  a  culmination  in  May. 
From  these  data  he  concludes  that  the  variations  of  memory 
agree  much  better  than  those  of  muscle  strength  with  those 
of  air  pressure.  The  curve  swings  up  and  down  during  No- 
vember and  December,  but  shows  a  rise  in  January.  In  con- 
clusion he  says  that  memory  is  probably  influenced  in  the 
same  way  as  muscle  strength  by  metreorological  conditions. 
(3)  EFFECTS  OF  VARIATIONS  IN  SUNLIGHT. 

Though  the  exact  effects  of  sunlight  on  the  human  organ- 
ism are  unknown,  much  has  been  written  about  its  stimu- 


70  PERIODIC   VARIATIONS    IN    EFFICIENCY 

lating  effects,  and  we  have  all  felt  its  power.  Dexter  sug- 
gests that  sunlight  and  clear  days  cause  an  excessive  amount 
of  "reserve  energy"  which  must  be  worked  off.  In  this  way 
he  accounts  for  the  excesses  of  assaults,  murders,  and  sui- 
cides on  sunny  days.  In  his  study  he  also  finds  that  there  are 
fewer  errors  in  banks  on  sunny  days,  indicating  that  sunny 
days  are  more  favorable  to  mental  work  than  cloudy  days. 

Lehman  and  Pedersen  after  a  thorough  and  systematic 
investigation  of  the  effects  of  sunlight  on  muscular  ability 
come  to  the  conclusion  that  next  to  temperature,  the  effects 
of  light  on  muscle  strength  are  more  pronounced  than  any 
other  one  cause.  They  measured  light  strength  with  a 
Steenstrup  Photometer  and  found  that  muscle  strength 
begins  to  rise  in  January  with  light  strength,  and  continues 
to  grow  with  it  until  July  when  the  good  effects  are  over- 
come by  the  bad  effects  of  excessive  summer  heat. 

(4)     EFFECTS  OF  CHANGES  IN  TEMPERATURE. 

1 I )  Introduction.    Perhaps  the  most  important  influence 
of  all  the  varied  weather  conditions  is  that  of  temperature. 
The  effects  of  extremes  of  heat  and  cold  are  well  known. 
If  our  bodies  are  too  long  exposed  to  a  low  temperature 
without  protection,  the  nervous  system  becomes  paralyzed 
and  death  ensues.     If  our  body  is  exposed  to  extreme  heat 
for  too  long  a  time,  discomfort,  sleepiness,  and  finally  a  heat 
stroke  results. 

(2)  Body  Temperature.     In  any  study  of  heat  effects 
on  human  life,  however,  the  body  temperature  is  perhaps  the 
most  important  factor.     In  spite  of  many  external  changes, 
this  remains  fairly  constant.     The  temperature  of  the  air 
surrounding  the  body  under  our  clothing  is  about  90°.    We 
keep  this  fairly  constant  by  wearing  a  greater  or  less  amount 
of  clothing.     The  average  body  temperature  remains  con- 
stant at  about  98.6°  F.  or  36°  Cent.     This  varies  with  in- 
dividuals, and  with  the  same  individual  on  different  days. 


WEATHER    INFLUENCES  71 

(3)  Benedict  and  Carpenter.3  These  investigators  found 
a  minimum  body  temperature  from  3  to  5  a.  m.,  a  marked  in- 
crease at  about  7  a.  m., '  a  slow,  steady  rise  through  the 
evening  to  the  minimum  at  from  3  to  5  a.  m.     They  also 
found  variations  in  the  body  temperature  of  one  subject  to  be 
2.29°  F.  on  the  first  day,  and  1.67°  F.  on  the  second  day. 

(4)  New  York  Commission.     This   commission   found 
that  the  body  temperature  of  subjects  living  at  home  at  8 
a.  m.,  was  high  if  the  preceeding  night  had  been  warm,  and 
low  if  the  preceeding  night  had  been  cool.    The  variation  was 
about  i°  F.  for  20°  F.  of  atmospheric  temperature. 

(5)  Burnham.5    Burnham  says  that  with  an  increase  in 
the  external  temperature  there  is  likely  to  be  a  rise  in  the 
bodily  temperature,  and  this  is  accompanied  by  an  increase 
in  metabolism.    Up  to  a  certain  optimum,  this  increases  the 
activity  and  the  efficiency  of  the  organism,  beyond  that,  the 
increase  in  metabolism  caused  by  increase  in  temperature 
brings   about   a   condition   where   the   oxidation   and   elim- 
ination   processes    are    not    sufficient    to    carry    off    the 
waste  products,  with  the  necessary  rapidity,  toxic  products 
accumulate,     and     thus      fatigue     comes     quickly.        Re- 
cent studies  indicate  that  the  cause  of  heat  stroke  and  sun 
stroke  is  an  abnormal  change  in  metabolism. 

(7)  Dexter.7     Dexter  reports  that  in  New  York  City 
when  school  room  temperature  was  below  68°  F.,  the  mis- 
demeanors were  below  normal,  from  69°  to  73°  F.  they  were 
about  normal,  while  in  a  temperature  of  79°  F.  they  were 
below  normal. 

(8)  Hines.18     Supt.  Hines,  of  Crawfordsville,  Ind.  re- 
ports the  following  in  regard  to  the  effects  of  various  class- 
room temperatures: 

80°  F.,  Class  restless  and  dull.  70°  F.,  Excellent  work. 
74°  F.,  Not  so  dull  as  above.      68°  F.,  Best  work  today. 
72°  F.,  Restless.  66°  F.,  Splendid  work. 


72  FESlODtC   VARIATIONS    IN    EFFICIENCY 

65°  F.,  Class  happy  and  full  60°  F.,   Too   cold    for   good 
of  work.  work. 

(a)  Influence  of  Temperature  on  Rapidity  of  Addi- 
tion. (L.  and  P.)26 

From  May,  1906,  to  February,  1907,  both  Lehman  and 
Pedersen  took  daily  tests  in  rapid  addition  each  morning 
either  before  or  after  the  dynamometric  measurements, 
there  being  seven  columns  of  50  one  place  numbers  in  each 
test.  The  results  were  then  compared  with  variations  in  air 
pressure,  light  strength,  and  temperature.  The  conclu- 
sions are  as  follows :  "Up  to  the  present  we  have  not  been 
able  to  show  any  dependence  of  rapidity  of  addition  on  light 
strength  or  air  pressure.  As  soon  as  the  small  variations  are 
effaced  by  taking  the  averages  for  each  five  days,  the  re- 
maining variations  show  themselves  almost  entirely  inde- 
pendent on  temperature."  The  results  are  shown  graphi- 
cally, and  indicate  that  when  temperature  sinks,  rapidity 
of  addition  rises,  and  vice  versa,  the  variation  in  rapidity 
of  addition  beginning  only  after  temperature  variation  has 
continued  a  short  time. 

(5)  EFFECTS  OF  VARIATIONS  IN  HUMIDITY. 
The  humidity  of  the  atmosphere  is  very  closely  related  to 
temperature  in  its  effects  on  human  life.  It  especially  effects 
the  body  in  its  efforts  to  maintain  a  constant  temperature. 
One  of  the  chief  means  for  keeping  the  temperature  of  the 
body  from  climbing  too  high  is  perspiration.  Whether  this 
takes  place  at  the  proper  rate  depends  as  much  on  the  hu- 
midity as  on  the  temperature.  Though  the  disagreeable 
effects  of  humidity  on  bodily  comfort  are  well  known,  they 
have  not  been  investigated  apart  from  temperature  to  any 
extent. 

The  New  York  Commission  found  that  bodily  tempera- 
ture was  lowered  by  confinement  in  an  atmosphere  of  68°  F, 


WEATHER    INFLUENCES  73 

with  50  per  cent,  relative  humidity,  that  it  was  raised  in  an 
atmosphere  of  75°  F.  with  the  same  humidity,  and  raised  still 
more  in  an  atmosphere  of  86°  F.  with  80  per  cent,  humidity. 
The  same  commission  found  the  average  pulse  rate  at  86°  F. 
with  80  per  cent,  humidity  to  be  74,  and  at  68°  F.  with  50 
per  cent,  humidity  to  be  66.  The  report  also  says,  ''Eastman 
and  I  have  seen  the  pulse  rate  increased  by  39,  form  67  to 
106,  as  the  temperature  of  the  surrounding  air  rose  from  74° 
to  110°  F.,  and  the  humidity  rose  from  50  to  90  per  cent. 
(Page  185). 

All  these  facts  would  indicate  that  excessive  humidity  not 
ority  causes  extreme  physical  discomfort,  but  that  it  has  a 
more  or  less  distinct  and  direct  influence  on  mental  and 
physical  efficiency. 

Dexter's  7  findings  seem  to  agree  with  the  above.  He 
found  that  a  low  humidity  caused  an  excess  of  occurrence- in 
nearly  all  classes  of  data  studied,  and  vice  versa. 

Kuhnes21  found  that  among  8  students,  the  best  work  was 
done  when  the  relative  humidity  was  from  75  to  85  per  cent., 
but  when  the  relative  humidity  fell  below  50  per  cent,  there 
was  a  marked  drop  in  efficiency. 

Huntington19  found  that  in  winter,  the  dampest  days  are 
unmistakably  the  times  of  greatest  efficiency.  "We  may 
shiver  when  the  air  is  raw,  but  we  work  well."  The  rea- 
son is  two-fold.  In  general  the  temperature  rises  in  times 
of  excessive  humidity  and  this  of  itself  is  favorable.  In 
spring  and  fall  when  the  temperature  ranges  from  freezing 
to  70°  F.  with  an  average  of  about  50°  F.  the  best  work 
is  done  with  a  relative  humidity  of  about  75  per  cent.  In 
other  words,  neither  dry  nor  wet  days  are  the  best.  The 
summer  curve  is  a  complex  one.  It  rises  first  to  a  maxi- 
mum at  60  or  65  per  cent.,  then  falls,  and  once, more  rises  to 
a  higher  maximum.  The  first  maximum  is  due  to  humidity, 
the  second  to  temperature.  A  hot,  damp  day  is  debilitating. 
The  majority  of  the  dampest  days  in  summer  are  compara- 


74  PERIODIC   VARIATIONS    IJT  EFFICIENCY 

tively  cool  for  they  accompany  storms.  The  coolness  coun- 
terbalances the  humidity  and  efficiency  increases.  Hence, 
we  conclude  that  with  an  average  temperature  of  60°  F.  to 
70°  F.,  a  relative  humidity  of  about  60  per  cent,  is  desirable." 

His  curves  also  show  a  diminution  of  work  in  dry  weather. 
This  evidently  has  a  bearing  on  the  low  level  of  the  curve  of 
energy  in  winter.  At  that  season  the  air  in  the  house  is  only 
1 6  to  20  per  cent,  relative  humidity,  and  it  should  be  60  to 
65  per  cent.  On  cold  days  the  percentage  is  still  lower.  It 
dries  up  the  mucious  membranes  and  is  favorable  to  colds, 
besides  producing  deaths  in  February  and  March. 
6.  EFFECTS  OF  BAROMETRIC  CHANGES. 

There  is  much  difference  of  opinion  as  to  the  effects  of 
barometric  changes.  The  general  idea  seems  to  be  that  of 
Dexter,  who  says  that  the  general  effect  of  high  altitudes  is 
undoubtedly  an  invigorating  one.  His  investigation  shows 
that  with  the  sole  exception  of  his  study  of  Errors  by  Bank 
Clerks,  a  low  barometer  is  favorable,  while  a  pressure  above 
the  normal  is  unfavorable. 

Lehman  and  Pedersen  on  the  contrary,  found  that  muscle 
strength  is  so  influenced  by  air  pressure  in  the  spring,  that  it 
rises  and  falls  with  the  same,  that  it  is  independent  of  air 
pressure  in  the  fall  up  to  the  end  of  November,  that  from 
December  to  March  the  variations  agree  more  and  more 
closely,  and  from  April  to  June  they  seem  to  agree  very 
closely.  After  June  there  seems  to  be  no  relation  till  De- 
cember. A  change  from  a  sea  level  to  a  height  where  air 
pressure  is  99  mm.  lower,  has  no  influence  on  muscle  strength, 
neither  is  muscle  strength  influenced  by  a  continued  stay  at 
such  a  height.  A  return  to  the  sea  level,  however,  causes  a 
more  or  less  noticeable  rise  in  muscle  strength,  according 
to  the  temperature,  but  it  lasts  only  a  short  time.  These  ef- 
fects are  shown  in  the  following  table,  where  the  averages  of 
the  positive  and  negative  deviations  of  muscle  strength  of 


WEATHER    INFLUENCES  75 

Lehman  on  two  different  years,  Miss  J.  and  the  Boys'  class 
are  compared  with  the  barometric  readings. 
Barometric  Readings     L  1905      L  1906      Miss  J.       Boys 
Above   763  +0.09      +0.28       +0.47       +0.15 

Below    762  —0.03       —0.17       —044       —0.49 

Kuhnes  found  that  of  8  test  persons,  6  were  at  their  best 
when  the  barometer  was  .10  above  normal,  and  one  each 
at  .10  and  .20  below  normal,  though  in  each  of  these  cases, 
the  second  best  record  was  at  .10  above  normal  also.  It 
would  seem,  therefore,  that  a  barometer  slightly  above  nor- 
mal is.  beneficial  to  muscle  strength. 

7.     SUMMARY  OF  PROBLEMS  AND  RESULTS  IN  WEATHER 
EFFECTS. 

There  seems  to  be  very  little  doubt  that  both  mental  and 
physical  energy  is  influenced  by  the  character  of  the  climate 
in  general,  wind,  sunshine,  temperature,  humidity,  and  air 
pressure,  though  the  exact  effects  are  still  somewhat  uncer- 
tain. 

1 i )  Precipitation.     Some  authors  find  that  precipitation 
has  little  or  no  effect.     This  is  the  view  of  Dexter.  Hunt- 
ington  finds  that  physical  efficiency  is  high  at  the  close  of  a 
storm. 

(2)  Winds.     Dexter  finds  that  calm  weather  results  in 
decrease  in  vitality,  while  moderate  winds  and  high  winds 
cause  vitality   to   increase   to   a   certain   point.      Excessive 
winds  cause  a  decrease  in  vitality. 

(3)  Character  of  the  Day.    The  effects  of  various  kinds 
of  days  on  mental  and  physical  abilities  seems  to  be  con- 
trary to  general  opinion.    Dexter  suggests  in  one  place  that 
sunlight  and  clear  days  cause  an  excessive  amount  of  re- 
serve energy,  and  must  be  worked  off.     In  another  he  finds 
that  for  all  the  data  studied,  except  deaths,  sickness,  and  er- 
rors in  banks,  cloudy  days  are  more  favorable  than  fair  days. 
He  was  surprised  to  find  more  suicides  on  cloudy  days  than 


76  PERIODIC    VARIATIONS    IN    EFFICIENCY 

on  days  with  precipitation,  and  more  on  fair  days  than  on 
either  of  the  others. 

Lehman  and  Pedersen  found  that  next  to  temperature  the 
effects  of  light  were  more  pronounced  than  any  other  cause. 
Huntington  found  that  people  are  least  efficient  in  work  on 
clear  days,  moderately  efficient  on  cloudy  and  partly  cloudy 
days,  and  most  efficient  at  the  end  of  a  storm.  He  also  finds 
that  ability  to  work  on  the  first  clear  day  is  very  poor,  the 
second  and  third  clear  days  are  better,  the  first  cloudy  days 
when  storms  start  are  medium,  and  from  the  second  to  the 
last  of  a  series  of  stormy  days,  when  storms  break,  is  very 
high. 

(4)  Temperature.  Changes  of  temperature  are  perhaps 
the  most  important  of  all  atmospheric  influences,  and  operate 
directly  by  causing  changes  in  the  body  temperature.  The 
body  temperature  must  be  kept  fairly  constant  at  about 
98.6°  F.  This  has  been  found  to  vary  slightly  with  different 
individuals  and  in  the  same  individual  on  different  days. 
Benedict  and  Carpenter,  and  another  investigator,  Polio- 
manti,33  find  a  daily  rhythm  of  body  temperature,  starting 
from  the  lowest  point  between  3  and  5  a.  m.,  showing  a  sharp 
rise  at  7  a.  m.  and  a  slow,  steady  rise  through  the  day,  cul- 
minating between  3  and  6  p.  m.,  then  falling  slowly  to  the 
minimum  between  3  and  5  a.  m. 

Lehman  and  Pedersen  find  that  when  the  temperature 
sinks  rapidity  of  addition  rises,  and  vice  versa,  the  variation 
of  rapidity  of  addition  beginning  only  after  the  temperature 
variation  has  continued  a  short  time.  They  also  suggest 
that  each  person  has  a  temperature  optimum  differing  for 
mental  and  for  physical  work,  and  that  the  abilities  increase 
as  the  temperature  nears  the  optimum  either  from  above  or 
below. 

Huntington  located  the  optimum  for  physical  work  be- 
tween 59°  and  65°  F.,  while  Lehman  and  Pedersen  locate 


77 

theirs  at  54°  and  59°  F,  respectively.    Students  at  Annapolis 
worked  best  when  the  outside  air  was  40°  F. 

Burnham5  says,  there  is  apparently  an  optimum  tempera- 
ture for  all  forms  of  activity,  fixing  it  in  man  at  an  outdoor 
temperature  of  60°  F.  for  physical  activity,  and  at  40°  F. 
for  mental  activity.  Concerning  ventilation  of  school  rooms, 
Burnham  states  that  the  primary  purpose  of  ventilation  is  to 
maintain  an  optimum  temperature,  and  concludes  that  the 
optimum  temperature  for  a  school  room  seems  to  be  about 
68°  F.  with  a  relative  humidity  of  about  50  per  cent. 

(5)  Humidity.     Humidity  especially  affects  the  body  in 
its  efforts  to  maintain  an  optimum  temperature  by  its  in- 
fluences over  the  amount  of  perspiration.    Huntington  finds 
that  "in  winter,  the  dampest  days  are  best ;  in  spring  and  fall 
when  the  average  temperature  is  about  50°  F.  we  work  best 
with  a  relative  humidity  of  about  75  per  cent. ;  and  in  dry 
weather  there  is  a  diminution  in  the  amount  of  work  done. 

Dexter  found  that  a  low  humidity  caused  an  excess  of 
occurrence  of  nearly  all  classes  of  data  studied,  and  vice 
versa.  Kuhnes  found  that  the  best  work  was  done  when 
the  relative  humidity  was  from  75  to  85  per  cent. ;  but  when 
the  relative  humidity  fell  below  50  per  cent,  there  was  a 
marked  drop  in  physical  efficiency. 

(6)  Barometer.  The  general  opinion  concerning  the  in- 
fluence of  barometric  changes  seems  to  be  that  of  Dexter, 
that  a  low  barometer  and  high  altitudes  are  favorable  to 
mental  and  physical  activities.     On  the   contrary,   Kuhnes 
found  that  a  barometric  pressure  of  about  .10  above  normal, 
with   slight  individual   differences,   seemed  to  be   the  most 
favorable,  and  Lehman  and  Pedersen  also  found  an  increased 
efficiency  with  high  barometric  pressure.     They  also  found 
that  a  change  from  sea  level  to  higher  land  has  no  influence, 
but  that  on  a  return  to  the  sea  level,  a  more  or  less  noticeable 
rise  occurs   which  varies  with  the  temperature  conditions. 
They  claim  that  in  the  spring,  muscle  strength  rises  and  falls 


78  PERIODIC   VARIATIONS    IN 

with  the  barometer,  that  they  separate  in  July,  and  are  in- 
dependent till  December,  when  they  begin  to  agree  more 
and  more  closely,  coming  into  very  close  agreement  in  March. 

8.     WEATHER  EFFECTS  IN   MY  ORIGINAL  EXPERIMENTAL 

INVESTIGATION. 

( I )  Character  of  the  Day.  In  order  to  study  the  effects 
of  the  general  character  of  the  day  I  have  used  the  U.  S. 
Government  Weather  Reports  and  arranged  the  days  of  the 
month  under  the  three  heads  of  clear,  partly  cloudy,  and 
cloudy  in  the  accompanying  tables. 

AVERAGES  OF  RIGHT  HAND  GRIPS 

Month  Oct.      Nov.     Dec.     Jan.      Feb.      Mch.     Apr.  May 

Clear    Days          45.8      49.8      52.5      53.8      54.2      54.6      55.9  58.8 

Ptly.    Cldy.  46.2      50.5      54.9      53-8      54-4      55         56.9  59-6 

Cloudy  46.8      49.3      52.8      54.7      54         54.6      56.1  58 

AVERAGES  OF  LEFT  HAND  GRIPS 

Month               Oct.      Nov.     Dec.      Jan.      Feb.      Mch.  Apr.  May 

Clear  Days           42.3      46.8      50.2      50.5      50.9      52.6  53.6  55.4 

Ptly.  Cldy.            43-1   .  47.2      53.6      52.4      51.3      53.2  55.5  57.3 

Cloudy                  42.6      46.2      49.4      51.8      50.5      52.5  54.2  55.8 

These  tables  show  that  partly  cloudy  days  are  the  most 
favorable  for  muscle  strength,  that  cloudy  days  are  next,  and 
that  clear  days  are  least  favorable.  In  the  three  months, 
November,  February,  and  May,  it  appears  that  cloudy  days 
are  slightly  less  favorable  than  clear  days.  An  examination 
of  the  original  data,  however,  shows  that  in  November  all  the 
cloudy  days  were  in  the  first  half  of  the  month,  and  as  there 
was  a  large  increase  in  November  the  seeming  advantage  of 
the  clear  days  disappear.  In  May  also,  the  only  two  days 
called  cloudy,  come  in  the  first  week  of  May  so  that  the 
advantage  of  the  clear  days  disappears  here  as  well  In 
February  the  low  record  for  cloudy  days  is  caused  by  low 
averages  on  two  days,  February  7  and  13,  in  the  right  hand. 
In  each  case  the  low  daily  average  is  due  to  a  remarkably 
low  mark  by  two  boys  of  the  group.  During  the  months  of 


79 

January,  February,  and  March,  it  was  not  unusual  for  a  boy 
to  drop  from  3  to  5  Kg.  for  a  day  or  for  a  week,  and  as  sud- 
denly recover  his  efficiency.  The  low  marks  above  are  such 
special  cases.  We  are,  therefore,  justified  in  the  conclusion 
that  partly  cloudy  days  are  the  most  favorable  to  muscle 
strength,  cloudy  days  next,  and  clear  days  least  favorable. 

In  the  table  for  the  Mental  Tests,  the  advantage  of  the 
cloudy  and  partly  cloudy  over  clear  days  is  not  so  marked. 

MEMORY  TEST  AVERAGES 

Month  Oct.  Nov.      Dec.     Jan.      Feb.      Mq'h.     Apr.     May 

Clear  Days  94      10.4      10.8      n.i       10         10.6      11.3      11.2 

Ptly.  Cldy.  10.2      10.4-     u.i       10         10.2      10.2      10.9      11 

Cloudy  Days          9.3      10.7      10.9      10.6      10.2      10.6      11.4      11.5 

Here  we  see  a  small  advantage  for  cloudy  days  in  every 
month  except  January,  and  as  in  the  muscle  tests  we  find 
January,  February,  and  March  to  be  a  time  of  unusual  re- 
sults. The  unusually  high  average  for  clear  days  in  January 
is  due  to  especially  high  scores  on  January  9,  where  two  boys 
scored  15,  and  two  14;  and  on  January  8,  where  one  boy  got 
15,  and  three  boys  13  points  each. 

From  the  above  data,  therefore,  we  are  warranted  in  con- 
cluding that  cloudy  and  partly  cloudy  days  are  rarely  a 
disadvantage,  and  that  they  may  be  positively  advantageous 
to  both  physical  and  mental  activities. 

(2)     Temperature,  Humidity,  and  Light  Strength. 

In  the  tables  where  the  weekly  averages  of  the  grip 
strength  and  memory  records  are  compared  with  the  weather 
variations,  we  find  some  variations  in  efficiency  seem  to  be 
due  to  changes  in  temperature,  humidity,  and  light  strength, 
or  to  various  combinations  of  them.  In  general,  the  results 
for  muscle  strength  show  a  rising  tendency  in  the  fall  as  the 
temperature  decreases,  a  period  of  arrest,  while  the  tempera- 
ture is  low,  and  a  tendency  to  increase  with  increasing  light 
strength  from  the  first  of  March,  which  is  aided  by  rising 
temperature  from  the  first  of  April  to  the  end  of  the  tests  in 


8O  PERIODIC    VARIATIONS    IN    EFFICIENCY 

June.  These  are  the  same  variations  which  Lehman  and 
Pedersen  found  in  their  study.  A  question  might  be  raised 
as  to  why  light  strength  should  not  have  influenced  muscle 
strength  earlier  in  the  year.  A  glance  at  the  tables,  however, 
shows  the  reason  why  this  is  delayed.  From  the  first  of 
January  to  the  last  of  February,  we  find  only  1 1  clear  days, 
and  a  relative  humidity  of  from  75  to  100  per  cent,  on  all  but 
four  of  the  days  during  that  time.  This  would  indicate  a 
long  season  of  cold,  damp  weather,  with  a  soft,  and  muddy 
soil,  a  time  when  the  boys  would  not  take  much  outdoor 
exercise,  and  when  their  vitality  would  probably  be  very  low. 
That  this  is  true  is  also  shown  by  the  fact  that  in  this  season 
of  the  year  we  find  the  only  time  when  the  average  strength 
on  clear  days  shows  a  superiority  over  that  on  cloudy  days. 
It  would  further  seem  that  cold  weather  with  excessive  hu- 
midity is  unfavorable  for  muscle  strength  on  account  of  its 
direct  effects  on  the  temperature  of  the  human  body. 

The  data  also  show  that  while  a  moderately  high  humid- 
ity is  favorable  for  temperatures  of  from  40°  to  80°  F.,  it  is 
unfavorable  when  the  temperature  is  below  that  point.  Sev- 
eral instances  may  also  be  found  in  the  records  where  a  drop 
in  the  temperature  accompanied  by  a  rise  in  the  humidity, 
caused  a  decrease  in  muscle  strength,  and  an  increase  in 
memory  ability. 

From  a  search  among  the  individual  records,  we  find 
that  while  the  whole  group  did  not  lose  in  physical  and 
mental  efficiency  at  the  same  time,  they  all  experienced  a 
more  or  less  pronounced  slump  sometime  between  the  middle 
of  December  and  the  first  of  April.  Two  of  the  ten  began  to 
slump  in  December,  the  other  eight  begining  in  January,  and 
they  all  last  from  three  to  ten  weeks.  In  the  A.  division,  for 
the  grips,  five  begin  to  slump  in  December,  fourteen  in  Janu- 
ary, and  three  in  February. 

It  is  very  evident,  therefore,  that  there  are  some  causes 
at  work  which  cause  a  decrease  in  physical  efficiency  during 


WEATHER  INFLUENCES  81 

the  months  of  December,  January,  and  February,  and  twc 
months  of  cold,  cloudy,  damp  weather  with  low  temperatures 
and  high  humidity,  are  undoubtedly  among  the  causes. 


CHAPTER  VII. 

CRITICAL  REVIEW  OF  EXPERIMENTAL  METH- 
ODS IN  INVESTIGATING  PERIODICITY 

(i)  INTRODUCTION.  We  have  seen  that  both  mental  and 
physical  activities  are  far  from  being  constant,  and  that 
there  are  many  factors  which  seem  to  have  a  causal  relation 
to  them.  While,  as  a  whole,  both  the  mental  and  physical 
tests  show  many  irregularities,  there  are  many  rhythmic 
periods  shown  in  the  results.  The  causal  factors  which  pro- 
duce these  variations  are  sometimes  very  obscure.  In  addition, 
many  other  factors  appear  in  an  investigation  of  this  kind 
which  tend  to  produce  variations  in  the  data,  such  as  ma- 
terials, procedure,  methods  of  checking,  and  treatment  of 
results. 

There  are  often  so  many  peculiarities  in  the  records  for  a 
group,  that  it  is  frequently  difficult  to  account  for  them  in  any 
other  way  except  individual  differences.  The  following  rec- 
ords for  the  week  from  March  13  to  17,  all  taken  at  2  p.  m., 
with  little  difference  externally  in  temperature,  or  humidity 
(high  on  Friday),  are  typical  of  the  results  and  show  the 
difficulties  in  discovering  causes  by  comparisons  of  varia- 
tions. 


Subject     March  13 

March  14 

March  15 

March  16 

March  17 

Ba 

4 

3 

3  10 

4 

3 

5  12 

3    4 

5  12 

4 

5 

615 

2 

4 

3    9 

Be 

4 

5 

6iS 

4 

4 

3  ii 

2      2 

4    8 

4 

3 

5  12 

4 

3 

i     8 

Ch 

4 

i 

5  10 

4 

5 

4  13 

4    4 

5  13 

3 

4 

4  ii 

4 

5 

4  13 

Cu 

3 

5 

3  ii 

4 

5 

4  13 

4    2 

31   9 

4 

4 

i     9 

4 

3 

3  10 

Fr 

4 

3 

3  10 

4 

4 

5  13 

4    2 

i     7 

4 

3 

4  ii 

4 

3 

2    9 

Ke 

4 

5 

3  12 

3 

I 

2      6 

4    2 

5  ii 

4 

i 

o    5 

2 

3 

3    8 

La 

4 

3 

4  ii 

4 

i 

5  10 

3     i 

2      6 

4 

4 

4  12 

I 

4 

i    6 

Me 

4 

5 

3  12 

4 

5 

2    II 

4    3 

4  ii 

4 

3 

3  10 

4 

4 

4  12 

Mi 

4 

5 

4  13 

4 

3 

3  10 

4    4 

5  13 

4 

5 

3  12 

2 

5 

i    8 

Ru 

4 

i 

I     6 

4 

3 

2    9 

2     3 

.4    9 

4 

2 

4  10 

3 

3 

2      8 

82 

CRITICAL  REVIEW  83 

\  From  the  above  results  it  would  seem  that  unless  we  find 
a  variation  which  is  quite  general,  the  cause  is  very  difficult 
to  discover  except  by  statistical  and  graphic  methods,  and 
thus  we  are  never  sure  whether  similar  variations  show 
casual  effects  or  not.  No  doubt  the  excessive  humidity  on 
March  i/th  contributed  to  the  lowness  of  the  mark,  but  the 
fact  that  it  was  on  Friday,  and  St.  Patrick's  Day,  may  also 
have  influenced  the  results. 

(2)     DETAILED  DISCUSSIONS  OF  SCIENTIFIC  METHODS. 

In  any  experimental  investigation  concerning  periodicity 
as  shown  in  mental  and  physical  tests,  the  chief  things  to  be 
considered  are : 

i — Adaptability  of  means  to  the  end.  This  is  one  of  the 
first  requisites.  Any  neglect  here  is  sure  to  prove  a  prolific 
source  of  error.  As  a  test  of  physical  energy,  the  dynamo- 
metric  tests  seem  to  be  one  of  the  best  as  well  as  one  of  the 
easiest  to  make.  The  instrument  used,  the  Smedley  Dyna- 
mometer, is  also  admirably  adapted  to  the  use  for  which  it  is 
designed.  Its  light  weight,  as  well  as  its  adjustability  make 
it. an  ideal  instrument. 

As  to  the  reliability  of  the  mental  tests,  there  is  a  great 
variety  of  opinion.  Many  sorts  of  tests  have  been  devised, 
and  after  a  careful  study  of  the  field,  I  have  come  to  believe 
that  numbers  and  nonsense  syllables  make  the  best  materials 
for  immediate  memory  reproduction.  While  the  material 
may  be  criticised  on  the  ground  of  conflicting  associations, 
a  conscious  effort  was  made  to  avoid  such  associations  in 
making  up  the  materials.  In  addition  to  this,  the  numbers 
used  are  so  commonly  associated  with  their  spoken  name^; 
that  this  association  would  seem  to  be  dominant.  Because  of 
the  limited  time,  and  the  ease  of  making  them,  tests  for  the 
immediate  memory  of  a  series  of  two  place  numbers  were 
chosen  as  the  material  to  be  used  in  the  tests. 


84  PERIODIC  VARIATIONS'  IN  EFFICIENCY 

Primary  memory  tests  involve  both  attention  and  imme- 
diate memory,  so  that  the  presentation  of  the  material  is  im- 
portant. Perhaps  the  presentation  of  the  materials  was  such 
as  to  appeal  more  strongly  to  some  types  of  minds  than  to 
others,  but  as  the  variations  and  not  the  actual  score  was  to 
be  used,  this  defect  was  largely  ovejcome  by  a  uniform  pre- 
sentation of  the  materials.  At  best,  mental  abilities  are  very 
complex,  and  the  validity  of  the  results  depends  more  on  the 
uniformity  of  the  materials,  methods,  and  proceedure,  than 
on  any  other  factors,  in  making  the  tests.  Immediate  mem- 
ory is  so  universally  depended  upon  in  everyday  life,  that  its 
importance  for  the  mental  life  is  second  to  none.  We  con- 
clude, therefore,  that  though  the  tests  may  be  criticised, 
the  same  criticism  may  be  applied  to  almost  any  sort  of  re- 
liable mental  tests,  and  that  the  tests  used  are  about  as 
reliable  as  any  tests  yet  devised.  . 

2 — Uniformity  of  Materials.  While  some  of  the  tests  may 
have  been  slightly  more  difficult  than  others,  the  differences 
were  not  great.  This  would  perhaps  account  for  occasional 
differences,  of  the  whole  group  on  different  days,  and  for 
differences  in  the  memory  for  the  series  of  fours,  fives,  and 
sixes  for  the  same  day,  but  it  could  not  account  for  such  dif- 
ferences in  the  weekly  record  here  given,  where  one  boy's 
record  is  4,  5,  o,  and  anothers  is  3,  o,  6,  etc.,  on  the  same  day. 
As  differences  of  this  sort  are  much  more  common,  we  must 
conclude  that  differences  in  the  materials  caused  little  if  any 
of  the  variations  in  the  results. 

3 — Similarity  of  the  Materials.  There  may  perhaps  have 
been  some  associations  formed  in  the  first  series  of  four 
numbers  which  persisted  until  the  second  or  third  series,  but 
a  careful  search  in  the  original  records  shows  only  a  few 
errors  which  could  possibly  be  due  to  such  associations.  The 
elimination  of  all  such  associations  is  very  difficult.  Both 
Lobsien's  and  Gates'  materials  also  suffered  from  the  same 


CRITICAL    REVIEW  85 

causes.  While  this  defect  might  account  for  a  few  minor  er- 
rors, the  effects  should  not  be  over-estimated. 

4 — Time  of  the  Year.  Though  the  results  of  this  investi- 
gation seem  to  show  a  course  of  seasonal  periodicity,  it  is 
not  pronounced.  It  is  evident,  however,  from  almost  all 
studies,  that  there  is  a  lowering  of  abilities  beginning  some- 
time between  December  and  February,  and  that  the  periods 
from  October  to  December,  and  from  March  to  June,  are 
more  favorable  than  from  December  to  March  for  mental 
abilities.  This  agrees  practically  with  the  low  point  in  the 
miisde  tests,  and  shows  there  is  some  sort  of  relation  be- 
tween them.  In  this  test,  also,  the  memory  results  do  not  go 
contrary  to  those  for  muscle  strength  as  do  Schuyten's  and 
Lobsien's,  but  keep  their  level  all  through  to  the  end  of 
May.  It  may  be  true  that  the  time  of  the  year  is  not  a  real 
cause,  but  that  the  real  causes  are  changes  in  temperature, 
light  strength,  air  pressure,  humidity,  etc.,  but  they  are  so 
closely  related  that  for  all  ordinary  purposes  we  may  relate 
the  variations  in  the  results  to  the  seasons  of  the  year. 

5 — Time  of  the  Week.  Some  investigators  have  found 
variations  which  seem  to  correspond  to  the  time  of  the  week, 
though  the  results  of  this  investigation  do  not  seem  to  be 
much  affected  by  it.  The  effects  indicated  seem  to  be  due 
to  other  causes. 

6 — Hour  of  the  Day.  There  seems  to  be  no  doubt  about 
a  diurnal  course  of  efficiency,  and  it  must  always  be  taken 
into  account  by  those  who  conduct  investigations  concerning 
mental  and  physical  abilities.  Its  effects  are  quite  apparent 
in  the  records  shown  during  the  first  three  months  by  the 
B.  division.  Early  hours  are  never  so  favorable  as  later 
ones,  and  the  maximum  is  usually  found  in  the  afternoon. 

7 — Temperature.  Quick  temperature  changes,  unseason- 
able temperature,  and  extremes  in  either  direction  seem  to 
cause  a  drop  in  abilities,  while  slight  changes  seem  to  be 
beneficial.  There  are  grounds  for  believing  that  each  per- 


86  PERIODIC   VARIATIONS    IN 

son  is  affected  in  a  unique  way  by  variations  in  temperature, 
and  that  there  is  an  individually  varying  optimum  tempera- 
ture for  each  person.  The  bodily  temperature  is  very  closely 
related  to  outside  temperature  and  is  a  resultant  of  outside 
temperature,  humidity,  exercise,  ventilation,  food,  clothing, 
etc. 

In  these  tests  temperature  played  a  prominent  part.  All 
the  tests  were  made  in  a  large,  light,  airy  room,  with  a  ther- 
mostat set  at  67°  F.,  which  regulated  the  temperature  of  the 
room.  The  heating  and  ventilating  was  controlled  and  reg- 
ulated by  a  combination  of  the  plenum  and  exhaust  systems, 
and  three  kinds  of  air — hot  air,  outside  air,  and  air  passed 
over  steam  jets  to  regulate  the  humidity.  The  temperature 
conditions  in  these  tests  were  therefore  fairly  constant,  and 
kept  around  67°  F. 

8 — Humidity.  An  excess  of  moisture  or  a  lack  of  moist- 
ure in  the  air  seems  to  be  the  cause  of  low  efficiency  in  both 
mental  and  physical  tests,  though  in  this  as  well  as  in  tem- 
perature, there  seems  to  be  an  individually  varying  optimum. 
It  must  therefore  be  taken  into  account  in  any  study  on 
periodicity. 

9 — Air  Pressure.  A  change  in  air  pressure  does  not  seem 
to  produce  much  effect  on  either  mental  or  physical  activi- 
ties unless  it  is  continued  for  a  long  time. 

10 — Fatigue.    No  doubt  fatigue  is  an  efficient  cause  in  the 

ariations  of  both  mental  and  physical  abilities.     In  this  in- 

"vestigation,  however,  I  have  tried  to  eliminate  the  influence 

of  fatigue  variations  so  far  as  possible,  by  giving  short  tests 

always  at  the  same  hour  of  the  day.     It  is  of  course  to  be 

doubted  that  each  individual  was  equally  fatigued  at  the  same 

hour  each  school  day,  but  with  only  one  record  per  day,  we 

have  no  basis  for  discovering  its  influence. 

It  appears  from  other  studies  that  when  the  body  tempera- 
ture increases  above  the  optimum,  the  waste  products  are  not 


CRITICAL    REVIEW  87 

eliminated  fast  enough,  and  that  they  act  as  poisons,  dimish- 
ing  all  activity  and  that  fatigue  then  comes  on  rapidly. 
From  the  study  of  Gates,  we  see  also  that  one's  own  ideas  as 
to  his  abilities  are  not  always  reliable.  The  influence  of 
fatigue,  however,  cannot  be  excluded  from  these  results,  but 
it  must  remain  an  unanalyzed  factor  in  the  diurnal  course 
of  efficiency. 

ii — Daily  Habits.  Of  course  the  ability  of  an  individual 
may  be  influenced  by  many  daily  habits,  such  as  the  time  of 
rising,  time  of  eating,  character  and  quantity  of  the  food, 
clothing,  general  habits  of  work,  etc.,  but  in  such  a  study  as 
this,  the  effects  of  such  influences  are  very  difficult  to  dis- 
cover. 

12 — Practice  Effects.  In  the  physical  tests,  with  growing 
youths  for  subjects,  we  see  that  the  combination  of  growth 
and  practice  affects  the  results  considerably.  In  this  investi- 
gation, those  who  were  tested  five  times  weekly  gained  about 
twice  as  much  at  the  same  age,  as  those  tested  but  once 
weekly.  The  mental  tests,  however,  do  not  show  these  effects 
so  plainly.  It  is  probable  that  they  are  one  of  the  chief  causes 
for  the  fact  that  both  muscle  and  mental  abilities,  when  tested 
for  any  considerable  time,  show  rising  tendencies  through 
the  greater  part  of  that  time. 

13 — Exercise.  While  this  is  closely  related  to  practice 
effects  on  the  one  hand,  and  fatigue  on  the  other,  exercise 
has  an  effect  all  its  own.  It  is  especially  shown  that  physical 
tests  taken  before  and  after  exercise  show  an  increase  in 
efficiency,  and  that  rest  after  continuous  work,  either  mental 
or  physical,  increases  both  mental  and  physical  efficiency. 

14— Other  Individual  Differences.  There  are  many  other 
factors  involved  in  a  study  of  mental  and  physical  periodicity, 
such  as  age,  sex,  health,  working  habits,  rest  periods,  sleep, 
endurance,  pulse  rate,  blood  pressure,  etc.,  which  may  or  may 
not  influence  the  results  from  physical  and  mental  tests.  In 
these  tests,  where  we  must  limit  our  study  to  mass  results,  it 


88  PERIODIC    VARIATIONS    IN    EFFICIENCY 

is  well  to  recognize  possible  causes  even  though  we  cannot 
point  out  their  influence  in  any  particular  case. 

15 — Checking  the  Results.  In  any  statistical  study,  the 
checking  of  the  results  is  very  important.  Whe^n  physical 
tests  are  given  with  a  dynamometer,  the  results  are  at  once 
expressed  in  a  measurable  quantity.  It  is  otherwise  with  the 
results  from  the  mental  tests.  In  this  instance,  I  decided  to 
give  a  single  point  for  each  number  correctly  given  in  the 
proper  order,  one-half  a  point  for  a  correct  number  in  the 
wrong  order,  and  one-half  a  point  for  each  correct  digit  in 
the  right  place  and  order. 

The  next  question  was  which  number  series  to  count.  The 
four  series  was  good  but  too  short.  The  five  series  was  bet- 
ter, and  the  four  series  served  as  a  sort  of  preparation  for  the 
five  series.  The  six  series  was  rather  too  long,  but  it  gave 
an  opportunity  for  those  with  high  ability  to  use  all  of  it. 
After  considering  the  merits  of  each  of  the  three  series,  I 
decided  to  use  all  of  them,  for  though  they  were  quite  differ- 
ent, they  were  to  be  used  for  purposes  of  comparison.  But 
I  have  given  the  weekly  averages  for  each  of  the  number 
series  in  the  tables,  and  I  have  used  them  in  making  com- 
parisons with  the  weather.  The  results  from  all  three  prove 
to  be  very  similar  so  that  the  use  of  the  three  series  again 
justifies  itself. 

1 6 — Uniformity  of  procedure.  It  is  necessary  to  re- 
duce procedure  to  a  basis  of  strict  uniformity,  for  varia- 
tions in  procedure  may  cause  many  accidental  errors. 
Every  investigator  needs  to  have  preliminary  trials  or  tests, 
and  work  out  the  details  of  procedure  thoroughly  before 
starting  the  main  tests  upon  which  the  results  are  to  be 
based.  The  tests  should  always  be  taken  or  made  by  the 
same  person,  or  serious  differences  may  destroy  the  validity 
of  the  results. 

17 — Statistical  treatment.  In  taking  the  physical  abil- 
ities of  a  group,  both  the  median  and  the  average  are 


CRlflCAt   REVIEW  89 

commonly  used.  The  median  may  be  valuable  in  testing 
a  homogeneous  group  where  the  distribution  of  results  is 
important,  but  in  a  group  like  the  .ones  in  this  study, 
the  variations  are  more  important  than  the  distribution.  I 
have,  therefore,  used  the  averages.  In  the  mental  tests,  the 
median  is  perhaps  more  important  on  account  of  the  slight 
difference  in  ages,  or  in  the  study  of  a  single  test  person. 
The  median'  is  given  in  some  of  the  mental  tables,  but  for 
the  sake  of  comparisons,  the  main  thing  is  uniformity  of 
treatment,  therefore,  I  have  used  the  averages  throughhout 
in  making  the  comparisons. 

i  8f — Tabular  presentation.  The  tabular  presentation 
should  be  quite  complete,  showing  as  much  of  the  detail 
(5f  £Vie  data  as  possible.  Tables  should  organize  the  data 
so  that  certain  tendencies  will  appear  plainly,  and  they 
should  be  used  to  illustrate  the  facts  claimed  to  be  dis- 
covered or  proven  by  the  investigation.  The  chief  care, 
however,  should  be  to  give  the  complete  data,  so  that  others 
may  examine  in  detail  and  discover  whether  the  conclu- 
sions drawn  are  warranted  by  the  data. 

19 — Correlation  of  results.  While  a  correlation  ex- 
presses -a  certain  mathematical  relationship  between  two 
sets  of  data,  from  a  great -amount  of  work  we  get  only  a 
single  mathematical  expression  which  entirely  neglects  the 
details  of  the  study.  The  value  from  such  relationships  is 
purely  statistical,  and  the  presence  of  a  high  correlation 
proves  nothing. 

20 — Verifying  Tests.  It  is  always  valuable  when  possible 
to  conduct  a  series  of  verifying  tests,  in  order  to  discover 
whether  the  results  show  general  instead  of  special  tenden- 
cies, and  to  prove  the  results  of  the  real  tests.  In  this  in- 
vestigation, I  can  only  use  the  records  from  the  A.  Divi- 
sion for  that  purpose.  They  show  the  same  general  ten- 
dencies as  the  results  from  the  B.  Division  and  tend  to  add 
to  the  value  of  the  results. 


90  PERIODIC   VARIATIONS    IK    EFFICIENCY 

(3)  VALIDITY  OF  THE  RESULTS.  The  validity  of  the  re- 
sults depends  almost  entirely  on  the  choice  of  means  and 
materials,  and  on  the  degree  of  control  exercised  by  the 
experimenter  over  the  means,  methods  and  procedure. 
In  this  case,  the  means  were  a  typical  group  of  high  school 
boys  of  various  ages.  The  method  in  the  physical  tests 
was  one  which  has  been  used  many  times  for.  similar  pur- 
poses, and  extreme  care  was  used  by  the  experimenter  to 
keep  the  procedure  uniform.  The  results  from  the  physical 
tests  are  of  unusual  validity,  and  should  be  so  considered. 

The  means  used  in  the  mental  tests,  though  open  to 
criticism  in  minor  points,  are  perhaps  as  well  adapted  to  the 
purpose  as  any  which  had  been  devised  up  to  the  time  when 
this  experiment  was  made.  It  was  necessary  to  have  a 
series  of  mental  tests  that  would  not  consume  too  much  of 
the  student's  time,  and  one  that  would  be  of  about  uniform 
difficulty.  Nonsense  syllables  were  considered,  but  the  task 
of  making  a  sufficient  number  of  tests,  enough  to  last  for  a 
whole  school  year,  in  a  short  time,  was  too  great,  so  num- 
bers were  chosen.  By  using  two  place  numbers,  a  series 
of  three  hundred  mental  tests  was  made  from  materials 
which  are  so  common  that  associations  between  the  num- 
bers' were  lost  from  one  day  to  another,  and  in  this  way 
each  series  was  entirely  new  when  presented.  Then  again, 
the  results  from  the  memory  tests  are  not  expected  to  set 
standards  of  mental  ability,  but  to  furnish  data  for  com- 
parisons. They  can  therefore  be  used  for  that  purpose  to 
good  advantage,  and  for  purposes  of  comparison,  the  re- 
sults are  perfectly  valid. 


CHAPTER   VIII. 

SUMMARY  AND  SUGGESTIONS 

The    following    significant    facts    concerning    periodicity 
seem  to  be  indicated  by  the  results  of  my  investigation : 

(1)  There   are   three   distinct   periods    in   the   physical 
strength  of  growing  boys  in  the  course  of  a  school  year,  a 
period  of  growth  from  September  to  about  the  middle  of 
December,  a  period  of  depression  from  January  to  March, 
and  a  period  of  renewed  growth  from  March  to  June. 

(2)  There  are  also  three  more  or  less  distinct  periods  in 
mental  -energy  during  the  school  year,  the  curve  of  which 
tends  to  resemble  the  curve  for  physical  periodicity  in  the 
same   group   of   subjects:    first,    a    favorable    period    from 
September  to  the  end  of  the  year,  an  unfavorable  period 
from  January   to   March,   and   a   second    favorable   period 
irom  March  to  May. 

(3)  The  depression  in  mental  abilities  seems  to  appear 
somewhat  after  the  depression  in  physical  strength,  is  much 
less  noticeable,  and  does  not  last  so  long. 

(4)  The  period  of  depression  in  mental  and   physical 
abilities   comes   at   the  beginning   of   winter,  and   while   it 
shows  many  individual  variations,  it  occurs  in  all  subjects 
studied  and  lasts  from  three  to  six  weeks.    Adults  and  boys 
of  low  vitality  tend  to  show  it  early  in  December.     Young 
and  growing  boys  show  it  any  time  between  the  first  of 
December,  and  the  middle  of  January.    In  some  subjects  the 
effects  are  overcome  by  the  middle  of  February,  in  others  by 
March,  but  in  special  cases  it  sometimes  lasts  until  May. 

(5)  Sunlight  seems  to  affect  mental  and  physical  abili- 
ties favorably,  the  stronger  its  rays,  the  more  its  influence. 

(6)  Temperature  has  an  individually  varying  optimum, 

91 


92  PERIODIC    VARIATIONS    IN    EFFICIENCY 

so  that  both  the  lowest  and  the  highest  temperatures  have  a 
depressing  effect. 

(7)  The  larger  yearly  periodic  variations  in  mental  and 
physical  abilities  are  probably  due  in  a  large  part  to  the  com- 
bined influence  of  temperature  and  light  strength. 

(8)  Other  causal  factors  in  periodicity  are  food,  cloth- 
ing, body  temperature,  humidity,  air  pressure,  character  of 
the  day,  fatigue,  time  of  day,  practice  effects,  previous  men- 
tal and  physical  development,  mental  activity  toward  the 
activity  tested,  general  bodily  health,  and  various  individual 
differences. 

(9)  Changes  in  temperature  and  humidity  are  at  first 
seen  in  the  changed  body  temperature.     When  long  con- 
tinued, they  clearly  affect  both  physical  strength  and  mental 
abilities. 

(10)  There  is  nothing  in  the  twenty-eight  day  periods 
of  Malling-Hansen,  or  the  twenty-three     day     periods     of 
Fleiss-Svoboda. 

( 1 1 )  There  is  no  distinct  weekly  periodicity  as  shown  in 
the  mental  and  physical  tests.     While  Monday  seems  to  be 
more  variable  than  the  other  days  of  the  week,  in  general, 
the  changes  which  appear  from  day  to  day  seem  to  be  due  to 
other  causes  than  merely  the  time  of  the  week. 

(12)  There   is   a   distinct   diurnal   course   of    efficiency 
shown  in  both  the  mental  and  physical  tests.     Both  increase 
quickly  through  the  forenoon,  each  show^a  slight  decrease 
around  noon,  and  both  come  to  a  maximum  in  the  afternoon. 
That  for  mental  abilities  culminates  around  2  p.  m.,  while 
that  for  physical  abilities  often  comes  later  in  the  afternoon. 

(13)  Cloudy  and  partly  cloudy  days,  if  not  too  long  con- 
tinued, are  usually  more  favorable  to  both  muscle  strength 
and  mental  efficiency,  than  clear  days.    Cold,  cloudy  weather 
with  a  high  humidity,  when  continued  through  several  days, 
is  unfavorable  to  both  mental  and  physical  abilities. 


SUMMARY   AND   SUGGESTIONS  93 

(14)  In  general,  the  cyclonic  movements  of  the  air  which' 
precede  a  storm,  seem  to  be  favorable  to  muscle  strength, 
while  the  anti-cyclonic  air  movements  which  follow,  seem  to 
have  a  depressing  effect. 

(15)  The  existence  of  an  individual  optimum  in  tem- 
perature, in  air  pressure,  and  in  humidity,  which  is  most 
favorable   to   mental   and   physical   activities,    is    very   im- 
portant, and  should  be  further  investigated. 

(16)  Most  of  the  investigations  in  this  field  are  suf- 
fering from  the  effects  of  statistical  treatment  of  the  facts. 
Many  times,  more  can  be  learned  from  the  careful  study  of 
one  subject  than  from  the  statistical  treatment  of  the  re- 
sults from  a  large  number  of  subjects. 

(17)  There  is  need  of  many  careful  experimental  studies 
on  the  influence  of  various  climatic  conditions  and  atmos- 
pheric changes  on  individuals. 

(18)  There  is  need  of  many  more  investigations  con- 
cerning both  mental  and  physical  periodicity  where  the  con- 
ditions are  carefully  controlled. 


CHAPTER    IX. 

BIBLIOGRAPHY 

1.  Abbe,  A.    Humidity.    Cited  by  Titchener.    American  Journal  of 
Psychology,  Vol.  20,  1909. 

2.  Bagley,  W.    C.     Physiological   Age.       Psychological     Bulletin, 
1909,  p.  188. 

3.  Benedict,   F.   C.   and  Carpenter,  T.   M.     The   Metabolism  and 
Energy  Transformations  of  Healthy  Man  During  Rest.     Wash- 
ington, Carnegie  Institute,  1910. 

4.  Burke,    Frederick.      American    Journal    of    Psychology,    April, 
1898,  Vol.  9. 

5.  Burnham,  Wm.  H.     Optimum  Temperature  for  Mental  Work. 
Ped.  Sem.  Vol.  xxiv,  p.  53. 

6.  Christopher,  W.  S.       Report    on     Child     Study    Investigation. 
Reprint   from   the    Annual   Report   of    the    Chicago    Board    of 
Education.     Chicago,  1898-9. 

7-     Dexter,    E.    G.     Conduct    and    the    Weather..      Psych.    Review 
Monograph   Supplement,  Vol.  II.,   No.  6,  May,   1899. 

8.  Dexter,  E.  G.    The  Child  and  the  Weather.     Pedagogical  Sem- 
inary, Vol.  V.,  1895. 

9.  Dexter,  E.  G.      Weather    Influences.       Macmillan     Co.,     New 
York,  1904. 

10.  Finsen,  X.      Om    Periodiske    aarlige    Svingninger    i    Blodets 
Hamoglobenmangde,   Hospitchstiende,   1894. 

11.  Gates,  Arthur  I.     Variations  in  Efficiency  During  the  Day,  to- 
gether   with    Practice    Effects,    Sex    Differences,    and    Correla- 
tions.    Univ.  of  Cal.     Press.  1916. 

12.  Gates,  Arthur  I.     Diurnal  Variations  in  Memory  and  Associa- 
tions.    Univ.  of  Cal.  Press.  1916. 

13.  Gulick,  L.  H.     Discussion  of  Report  of  Committee  on  Variable 
Temperature.     Proceedings   of   the   American    School   Hygiene 
Association.  1912. 

14.  Hall,  G.  Stanley.    Adolescence,  Vol  I.  p.  21-23. 

15.  Hall,  Winifred.     Psychological  Bulletin,  1909. 

1 6.  Harley,  V.     The  Effects  of  Sugar  and   Smoking  on   Muscular 
Work.    Journal  of  Physiology,  Vol.  17,  1894. 

17.  Hill,    L.      Stuffy   Rooms:    facts    and    fancy    about    ventilation 
Popular  Science  Monthly,  Vol.  81,  1912. 

18.  Hines,    L.    N.      Effect   of    School   Room    Temperature   on   the 
Work  of  Pupils.    The  Psychological  Clinic.     Vol.  3,  1909. 

19.  Huntington.     Civilization   and  Climate.   Yale  University   Press, 
1916. 

94 


BIBLIOGRAPHY  95 

20.  Kraepelin,    E.      Zur    Hygiene     der      Arbeit.      Zeitschrift      ftir 
Psychiatric,  Vol.  25,  1898. 

21.  Kuhnes,  L.  L.     Variations   in   Muscular  Energy.     An  unpub- 
lished Thesis  for  Ph.D.  at  New  York  University,  1915. 

22.  Lee,    F.    S.     The    Effects    of   Temperature    and    Humidity   on 
Fatigue,  Amer.  Jour.  Pub.  Health,  Vol.  2,  1912. 

23.  Lee,   F.   S.     The  Recent   Progress   in   our   Knowledge   of  the 
Physiological    Action    of    Atmospheric    Conditions.      Science, 
Vol.  44,  1916. 

24.  Lehman,    A.     Die    Korperliche    Ausserungen    Psychischer   Zus- 
tande.      1899. 

25.  Lehman,    A.    and    Pedersen,    R.    H.      Das   Wetter   und   Unser 
Arbeit.     Archives  fur  die  Gesamte  Psychologic.     Vol.  10,  1907. 

26.. .  Lobsien,     Marx.     Schwankungen    der    Psychischen    Kapazitat. 
'Pedag.  Psychol.    Vol.  5,  1902. 

27.  Lobsien,   Marx.       Experimentelle     Untersuchungen     liber     die 
^Gedachtnissentwicklung     bei      Schulkindern.      Zeitschrift     fur 

Psych,  and  Physiol.  der  Sinneorgane.     Vol.  27,  1901. 

28.  Lombard,    W.    P.      Some    Influences    Affecting   the    Power    of 
Voluntary    Muscular    Contraction.      Journal    of     Physiology. 
Vol.  13,  1892. 

29.  Malling-Hansen.     Perioden  im  Gewicht  der  Kinder  und  in  der 

Sonnenwarme.     Copenhagen,    1886. 

30.  Marsh,  Howard  D.     The  Diurnal  Course  of  Efficiency.     Arch, 
of    Phil.,    Psych.,    and    Scicn.     Methods,    in    Columbia    Univ. 
Contrib.  to  Phil,  and  Psych.     Vol.  14,  1906. 

31.  Meumann,  Ernst.    Vorlesungen,  Vol.  I. 

32.  Patrici,  M.    Archives  Italiens  de  Biologic,  Vol.  17,  1892. 

33.  Poliomanti,   O.      Sopra   la   Possioilite   di   una   Inversions    della 
Temperature    Giornaliere    della    Roma.      Ziet    fur    Allgemeine 
Phys.    Vol.  16,  1914. 

34.  Robinson,  L.  A.       Mental     Fatigue     and     School     Efficiency. 
Winthrop  Normal  and  Industrial  Coll.  S.  C.  Vol.  5,  1912. 

35.  Schuyten,    M.    C.     Influence    des    variations    de    le    temperature 
atmospheriqtie    sur  Inattention   voluntaire   des   eleves.     Bull,   de 
IJAcad.    Roy.    des  Sciences,  des  Lettres,  et  des  Beaux  Arts  de 
Belgique,  Brussels,  1906.     Vol.  32. 

36.  Smith,  E.     Analysis  of  Respiration.     Proceedings  of  the  Royal 
Society  of  London,  Vol.  9,  1869. 

37.  Storey,    T.    A.      Studies    in    Voluntary    Muscular    Contraction. 
Stanford  University  Press.  1904. 

38.  Storey,  T.  A.     Some  Daily  Variations  in  Height,  Weight  and 
Strength,  Amer.  Boys.  Educ.  Review,  Vol.  7,  1902.- 

39.  Svoboda,   L.     Cited  by   Peters,  V.   Zeitschrift   fur  Psychology. 
1913.  P.  61  \. 


.   1JS  JL»U±i   UIN    TJUS 

STAMPED  BELOW 


AN  INITIAL  FINE  OF  25  CENTS 

WILL  BE  ASSESSED  FOR  FAILURE  TO  RETURN 
THIS  BOOK  ON  THE  DATE  DUE.  THE  PENALTY 
WILL  INCREASE  TO  SO  CENTS  ON  THE  FOURTH 
DAY  AND  TO  $I.OO  ON  THE  SEVENTH  DAY 
OVERDUE. 


SEP  27 


1931 


JflN  23  194) 


*5    g-1940 


FEB 


APft     22  1948 


LD  21-20m-5,'3 


488243 


I 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


